

A133658


Decimal expansion of Sum_{x=integer, inf < x < inf} (1/sqrt(2*Pi))*exp(x^2/2).


1



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

1,10


COMMENTS

Standard normal distribution taken at all integers x from infinity to +infinity.
Not only is this constant quite close to 1/tanh(pi^2) (difference is about 1.43*10^17), but it is even closer if the second term of its continued fraction, 186895766.612113..., is reduced by 1/2 (the difference then decreases to about 10^34).
The continued fraction begins: 1, 186895766, 1, 1, 1, 1, 2, 1, 2, 2, 1, 3, 1, 4, 1, 1, 1, 1, 1, 1, 1, 5, 4, 1, 6, 1, 5, 8, 1, 1, 3, 1, 44, 3, 7, 31, 2, 5, 1, 1, 5, 1, 5, 5334, 1, ...  Robert G. Wilson v, Dec 30 2007
See A084304 for cont.frac.(1/tanh(pi^2)) = [1, 186895766, 8, 1, 11, 2, 3, ...]  M. F. Hasler, Oct 24 2009


LINKS

G. C. Greubel, Table of n, a(n) for n = 1..10000


EXAMPLE

1.000000005350575982148479362482248...


MATHEMATICA

RealDigits[(1 + 2*Sum[ Exp[ x^2/2], {x, 1, 24, 1}])/Sqrt[2 Pi], 10, 2^7][[1]] (* Robert G. Wilson v, Dec 30 2007 *)


PROG

(PARI) default(realprecision, 100); sqrt(2/Pi)*(suminf(k=1, exp(k^2/2))+.5)
vecextract(eval(Vec(Str( % ))), "^2") \\ M. F. Hasler, Oct 24 2009


CROSSREFS

Sequence in context: A068116 A275836 A019172 * A267445 A071050 A271780
Adjacent sequences: A133655 A133656 A133657 * A133659 A133660 A133661


KEYWORD

cons,nonn


AUTHOR

Martin Raab, Dec 28 2007


EXTENSIONS

More terms from Robert G. Wilson v, Dec 30 2007


STATUS

approved



