George Pólya: If you want to climb the Matterhorn, you might first wish to go to Zermat, where those who have tried are buried.

—《黎曼博士的零点》引用了著名数学教育家波利亚的隐喻告诫

Practice what you preach, Practice makes perfect, Practice is the best mater.

“迎难而上”还是“知难而退”?

reporter: ” Why do you want to climb Mount Everest ? “

George Mallory: ” Because it’s there “

视死如归的乔治•马洛里在说过这话之后不久在珠峰上失踪，七十多年后其遗体被美国登山队员发现

—《千禧难题》引用了舍生忘死的英国登山家乔治•马洛里与随队记者之间这段毫不逊色于禅宗公案的对话

George Pólya: If you want to climb the Matterhorn, you might first wish to go to Zermat, where those who have tried are buried.

—《黎曼博士的零点》引用了著名数学教育家波利亚的隐喻告诫

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如今虽然阔别故乡多年了，但故土的一切烙在我的心中依旧那么鲜活。环顾四周的崇山峻岭一定还青山依旧，汹涌澎湃的金沙江一定还川流不息，交替更换着四季时装的祖传梯田一定还环簇着石头城，石头城一定还像只灵龟一样托负着半个村庄的父老乡亲。

石头城是老乡们心目中的图腾，地方志上把石头城比作天地间的一朵灵芝，这个比喻倒也妥贴。但在我看来，石头城更似天地间一朵圣洁的荷花，四周的山岭犹如花瓣，环抱石城的梯田恰如花壑，而石头城则是花蕊。

那里有我的童年，我曾来回穿行的小径，我曾战战兢兢扶着高粱杆走过的田埂，金沙江边的沙滩曾留下我“如同岁月了无痕”的脚印，那甘冽的山泉曾接受我的吮吻。

老人们一定在晴朗的冬日里悠闲地在石头城的城门口一面叙旧一面享受着日光浴，村子中心的小学一定还是全村庄最醒目的地标建筑，如同西方高大拔尖刺破青天的教堂。

自给自足的农耕生活一定还在故乡这片略显闭塞且偏僻崎岖的山地上延续。披星戴月的背上一定还背负着襁褓中的孩子，抑或篮筐。

乡亲们一定还在享用着开窍的核桃油，绿色无公害的有机蔬菜，不会甜得发腻的天然黄果，清汤犹鲜的江鱼，小农的生活也有高质量的一面。

故乡的夜色一定还那么别致，故乡的夜空一定还繁星密布，仿佛满天的星斗都簇拥在故乡那一片天上，小伙子小姑娘们一定还在朦胧的夜色中浪漫幽会。还有尘缘已尽已托体青山的祖先们，一定已融身青山化身山骨护佑着他们的后人。

清晨小学校的柳树下一定有成群的学子在念书，夜晚暗淡的灯光下一定有谁家的小孩在努力学习，他们会在不断的升学中成为故乡的游子，同时也是故乡的骄子，外出求学或外出工作。

爱着萦绕在心中的故乡的山、故乡的水、故乡的人，游子们或在他乡漂泊比如像我这等，或已经安居他乡。地球是咱家，何处不故乡？植身故乡想来乏味，人大都叶公好龙，总不能在一个地方呆一辈子，就像不能在一个小学永远留级下去毕不了业一样。心存故乡，离开故乡，人生就是如此。可怜的是老人们去世了据说都难能找到小伙子来抬灵柩了，土葬这个习俗固然不值得发扬光大，但老家上一辈的人还是希望用这种方式让他们能安详地离开这个尘世。

我曾熟悉那里的一切，心存百步一个地名的的故乡地图，乡音无改的母语腔调。故乡不只是一个地标，不只是那个经纬交叉标识的地域，故乡于我是心灵上念及瞬达的归宿。心中的故乡仿佛随时都可以置身其中身临其境，仿佛昨夜梦游故乡归来。

爱

让人与人

一见如故

爱

使心与心

没有距离

阳光暖身

爱暖心

爱比阳光更温暖

爱像星光一样璀璨

爱像月光一样皎洁

爱是心的光芒

心因爱而升华

爱让人如沐春风

爱让人如浴温泉

没有什么比爱

更让人幸福的了

I believe that I can best convey my thanks for the honour which the Academy has to some degree conferred on me, through my admission as one of its correspondents, if I speedily make use of the permission thereby received to communicate an investigation into the accumulation of the prime numbers; a topic which perhaps seems not wholly unworthy of such a communication, given the interest which and have themselves shown in it over a lengthy period.

For this investigation my point of departure is provided by the observation of that the product

if one substitutes for all prime numbers, and for all whole numbers. The function of the complex variable which is represented by these two expressions, wherever they converge, I denote by . Both expressions converge only when the real part of is greater than ; at the same time an expression for the function can easily be found which always remains valid. On making use of the equation

one first sees that

If one now considers the integral

from to taken in a positive sense around a domain which includes the value~ but no other point of discontinuity of the integrand in its interior, then this is easily seen to be equal to

provided that, in the many-valued function , the logarithm of is determined so as to be real when is negative. Hence

where the integral has the meaning just specified.

This equation now gives the value of the function for all complex numbers~ and shows that this function is one-valued and finite for all finite values of with the exception of , and also that it is zero if is equal to a negative even integer.

If the real part of is negative, then, instead of being taken in a positive sense around the specified domain, this integral can also be taken in a negative sense around that domain containing all the remaining complex quantities, since the integral taken though values of infinitely large modulus is then infinitely small. However, in the interior of this domain, the integrand has discontinuities only where becomes equal to a whole multiple of , and the integral is thus equal to the sum of the integrals taken in a negative sense around these values. But the integral around the value is , one obtains from this

thus a relation between and , which, through the use of known properties of the function , may be expressed as follows:

remains unchanged when is replaced by .

This property of the function induced me to introduce, in place of , the integral into the general term of the series , whereby one obtains a very convenient expression for the function . In fact

thus, if one sets

then

or since

I now set and

so that

or, in addition,

This function is finite for all finite values of , and allows itself to be developed in powers of as a very rapidly converging series. Since, for a value of whose real part is greater than , remains finite, and since the same holds for the logarithms of the other factors of , it follows that the function can only vanish if the imaginary part of lies between and . The number of roots of , whose real parts lie between and is approximately

because the integral , taken in a positive sense around the region consisting of the values of whose imaginary parts lie between and and whose real parts lie between and , is (up to a fraction of the order of magnitude of the quantity ) equal to ; this integral however is equal to the number of roots of lying within in this region, multiplied by . One now finds indeed approximately this number of real roots within these limits, and it is very probable that all roots are real. Certainly one would wish for a stricter proof here; I have meanwhile temporarily put aside the search for this after some fleeting futile attempts, as it appears unnecessary for the next objective of my investigation.

If one denotes by all the roots of the equation , one can express as

for, since the density of the roots of the quantity~ grows with only as , it follows that this expression converges and becomes for an infinite~ only infinite as ; thus it differs from by a function of , that for a finite~ remains continuous and finite and, when divided by , becomes infinitely small for infinite~. This difference is consequently a constant, whose value can be determined through setting .

With the assistance of these methods, the number of prime numbers that are smaller than can now be determined.

Let be equal to this number when is not exactly equal to a prime number; but let it be greater by when is a prime number, so that, for any at which there is a jump in the value in ,

If in the identity

one now replaces

one obtains

if one denotes

by .

This equation is valid for each complex value of for which . If, though, the equation

holds within this range, then, by making use of *Fourier*‘s theorem, one can express the function~ in terms of the function~. The equation decomposes, if is real and

into the two following:

If one multiplies both equations with

and integrates them from to , then one obtains on the right hand side in both, on account of *Fourier*‘s theorems; thus, if one adds both equations and multiplies them by , one obtains

where the integration is carried out so that the real part of remains constant.

For a value of at which there is a jump in the value of , the integral takes on the mean of the values of the function~ on either side of the jump. From the manner in which the function was defined, we see that it has the same property, and hence in full generality

One can substitute for the expression

found earlier; however the integrals of the individual terms of this expression do not converge, when extended to infinity, for which reason it is appropriate to convert the previous equation by means of integration by parts into

Since

for and therefore

it then follows that all the terms of the expression for , with the exception of

take the form

But now

and, if the real part of is larger than the real part of ,

or

depending on whether the real part of is negative or positive. One has as a result

in the first, and

in the second case.

In the first case the constant of integration is determined if one lets the real part of become infinitely negative; in the second case the integral from to takes on values separated by , depending on whether the integration is taken through complex values with positive or negative argument, and becomes infinitely small, for the former path, when the coefficient of in the value of becomes infinitely positive, but for the latter, when this coefficient becomes infinitely negative. From this it is seen how on the left hand side is to be determined in order that the constants of integration disappear.

Through the insertion of these values in the expression for one obtains

if in one substitutes for all positive roots (or roots having a positive real part) of the equation , ordered by their magnitude. It may easily be shown, by means of a more thorough discussion of the function~, that with this ordering of terms the value of the series

agrees with the limiting value to which

converges as the quantity increases without bound; however when re-ordered it can take on any arbitrary real value.

From one obtains by inversion of the relation

to obtain the equation

in which one substitutes for the series consisting of those natural numbers that are not divisible by any square other than~, and in which denotes the number of prime factors of .

If one restricts to a finite number of terms, then the derivative of the expression for or, up to a part diminishing very rapidly with growing ,

gives an approximating expression for the density of the prime number half the density of the squares of the prime numbers a third of the density of the cubes of the prime numbers etc. at the magnitude~.

The known approximating expression is therefore valid up to quantities of the order and gives somewhat too large a value; because the non-periodic terms in the expression for are, apart from quantities that do not grow infinite with :

Indeed, in the comparison of with the number of prime numbers less than , undertaken by *Gauss* and *Goldschmidt* and carried through up to three million, this number has shown itself out to be, in the first hundred thousand, always less than ; in fact the difference grows, with many fluctuations, gradually with . But also the increase and decrease in the density of the primes from place to place that is dependent on the periodic terms has already excited attention, without however any law governing this behaviour having been observed. In any future count it would be interesting to keep track of the influence of the individual periodic terms in the expression for the density of the prime numbers. A more regular behaviour than that of would be exhibited by the function , which already in the first hundred is seen very distinctly to agree on average with .

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