

A013661


Decimal expansion of zeta(2) = Pi^2/6.


80



1, 6, 4, 4, 9, 3, 4, 0, 6, 6, 8, 4, 8, 2, 2, 6, 4, 3, 6, 4, 7, 2, 4, 1, 5, 1, 6, 6, 6, 4, 6, 0, 2, 5, 1, 8, 9, 2, 1, 8, 9, 4, 9, 9, 0, 1, 2, 0, 6, 7, 9, 8, 4, 3, 7, 7, 3, 5, 5, 5, 8, 2, 2, 9, 3, 7, 0, 0, 0, 7, 4, 7, 0, 4, 0, 3, 2, 0, 0, 8, 7, 3, 8, 3, 3, 6, 2, 8, 9, 0, 0, 6, 1, 9, 7, 5, 8, 7, 0
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OFFSET

1,2


COMMENTS

Sum_{m = 1..inf } 1/m^2.
"In 1736 he [Leonard Euler, 17071783] discovered the limit to the infinite series, Sum 1/n^2. He did it by doing some rather ingenious mathematics using trigonometric functions that proved the series summed to exactly Pi^2/6. How can this be? ... This demonstrates one of the most startling characteristics of mathematics  the interconnectedness of, seemingly, unrelated ideas."  Clawson
Also dilogarithm(1).  Rick L. Shepherd, Jul 21 2004
Also Integral_{x=0..inf} x/(exp(x)1).
For the partial sums see the fractional sequence A007406/A007407.
Pi^2/6 is also the length of the circumference of a circle whose diameter equals the ratio of volume of an ellipsoid to the circumscribed cuboid. Pi^2/6 is also the length of the circumference of a circle whose diameter equals the ratio of surface area of a sphere to the circumscribed cube.  Omar E. Pol, Oct 07 2011
1 < n^2/(eulerphi(n)*sigma(n)) < zeta(2) for n > 1.  Arkadiusz Wesolowski, Sep 04 2012


REFERENCES

M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards Applied Math. Series 55, 1964 (and various reprintings), p. 811.
R. Calinger, "Leonard Euler: The First St. Petersburg Years (17271741)," Historia Mathematica, Vol. 23, 1996, pp. 121166.
Calvin C. Clawson, Mathematical Mysteries, The Beauty and Magic of Numbers, Perseus Books, 1996, p. 97.
W. Dunham, Euler: The Master of Us All, The Mathematical Association of America, Washington, D.C., 1999, p. xxii.
Michael D. Hirschhorn, A simple proof that zeta(2) = Pi^2/6, The Mathematical Intelligencer 33:3 (2011), pp 8182.
G. F. Simmons, Calculus Gems, Section B.15,B.24 pp. 2701,3235 McGraw Hill 1992.
A. Weil, Number theory: an approach through history; from Hammurapi to Legendre, Birkhaeuser, Boston, 1984; see p. 261.
David Wells, The Penguin Dictionary of Curious and Interesting Numbers, Revised Edition, Penguin Books, London, England, 1997, page 23.


LINKS

Harry J. Smith, Table of n, a(n) for n = 1..20000
M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards, Applied Math. Series 55, Tenth Printing, 1972 [alternative scanned copy].
D. H. Bailey, J. M. Borwein and D. M. Bradley, Experimental determination of Ap'erylike identities for zeta(4n+2)
P. Bala, New series for old functions
David Benko and John Molokach, The Basel Problem as a Rearrangement of Series, The College Mathematics Journal, Vol. 44, No. 3 (May 2013), pp. 171176.
R. Chapman, Evaluating Zeta(2):14 Proofs to Zeta(2)= (pi)^2/6
R. W. Clickery, Probability of two numbers being coprime [Broken link]
L. Euler, On the sums of series of reciprocals
L. Euler, De summis serierum reciprocarum, E41.
Math. Reference Project, The Zeta Function, Zeta(2)
Math. Reference Project, The Zeta Function, Odds That Two Numbers Are Coprime"
R. Mestrovic, Euclid's theorem on the infinitude of primes: a historical survey of its proofs (300 BC2012) and another new proof, arXiv preprint arXiv:1202.3670, 2012
J. Perry, Prime Product Paradox
Simon Plouffe, Plouffe's Inverter, Zeta(2) or Pi**2/6 to 100000 digits
Simon Plouffe, Zeta(2) or Pi**2/6 to 10000 places
A. L. Robledo, PlanetMath.org, value of the Riemann zeta function at s=2
E. Sandifer, How Euler Did It, Estimating the Basel Problem
E. Sandifer, How Euler Did It, Basel Problem with Integrals
C. Tooth, Pi squared over six
Eric Weisstein's World of Mathematics, Riemann Zeta Function 2
Eric Weisstein's World of Mathematics, Dilogarithm MathWorld page
H. Wilf, Accelerated series for universal constants, by the WZ method
Index entries for zeta function.


FORMULA

Limit(n>+oo) of (1/n)*(sum(k=1, n, frac((n/k)^(1/2)))) = zeta(2) and in general have limit(n>+oo) of (1/n)*(sum(k=1, n, frac((n/k)^(1/m)))) = zeta(m), m >= 2.  Yalcin Aktar, Jul 14 2005
Equals integral_(x=0..1) ((log(x)/(x1)) or integral_(x=1..infinity) (log(x/(x1))/x).  JeanFrançois Alcover, May 30 2013
From Peter Bala, Dec 01 2013: (Start)
Lim {n > inf} sum {k = 1..n1} (log(n)  log(k))/(n  k).
Also integral {x = 0..1} z^(z^(z^(...))) dx, where z = x^(x). (End)
From Peter Bala, Dec 10 2013: (Start)
zeta(2) = (16/9)*Sum_{n even} n^2*(n^2 + 1)/(n^2  1)^3.
zeta(2) = 3*sum {n >= 1} (20*n^2  8*n + 1)/( ((2*n)*(2*n  1))^2*C(4*n,2*n) ).
zeta(2) = 3*sum {n >= 1} (1701*n^4  1944*n^3 + 729*n^2  96*n + 4)/( ((3*n)*(3*n  1)*(3*n  2))^2*C(6*n,3*n) ) (Bala, Section 6).
See A108625 for series and continued fraction expansions for zeta(2) associated with the crystal ball sequences for the A_n lattice. See also A142995 and A142999. (End)
For s >= 2 (including Complex), zeta(s) = product {n >= 1} prime(n)^s/(prime(n)^s  1).  Fred Daniel Kline, Apr 10 2014
Also equals 1+sum_(n>=0) (1)^n*StieltjesGamma(n)/n!  JeanFrançois Alcover, May 07 2014


EXAMPLE

1.6449340668482264364724151666460251892189499012067984377355582293700074704032...


MATHEMATICA

RealDigits[N[Pi^2/6, 100]][[1]]


PROG

(PARI) \p 200; Pi^2/6
(PARI) \p 200 dilog(1) \p 200 zeta(2)
(PARI) a(n)=if(n<1, 0, default(realprecision, n+2); floor(Pi^2/6*10^(n1))%10)
(PARI) { default(realprecision, 20080); x=Pi^2/6; for (n=1, 20000, d=floor(x); x=(xd)*10; write("b013661.txt", n, " ", d)); } \\ Harry J. Smith, Apr 29 2009
(Maxima) fpprec : 100$ ev(bfloat(zeta(2)))$ bfloat(%); /* Martin Ettl, Oct 21 2012 */


CROSSREFS

Cf. A013679, A013631, A013680, 1/A059956. A108625, A142995, A142999.
Sequence in context: A201587 A110756 A200698 * A209273 A019174 A019166
Adjacent sequences: A013658 A013659 A013660 * A013662 A013663 A013664


KEYWORD

cons,nonn,nice


AUTHOR

N. J. A. Sloane


STATUS

approved



