

A009403


Expansion of e.g.f. log(1+tanh(x)^2), even powers only.


2



0, 2, 28, 992, 69088, 8110592, 1448424448, 366436769792, 124760831684608, 55014520738414592, 30501848618302701568, 20768078187214502100992, 17035983844637174375907328, 16570619538920401323784404992
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OFFSET

0,2


LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..100


FORMULA

a(n) ~ (1)^(n+1) * 2^(4*n) * (2*n)! / (n * Pi^(2*n)).  Vaclav Kotesovec, Apr 20 2014


MATHEMATICA

With[{nn=30}, Take[CoefficientList[Series[Log[1+Tanh[x]^2], {x, 0, nn}], x] Range[0, nn]!, {1, 1, 2}]] (* Harvey P. Dale, Aug 27 2013 *)


CROSSREFS

Cf. A024299.
Sequence in context: A012725 A264637 A012756 * A026944 A296464 A292806
Adjacent sequences: A009400 A009401 A009402 * A009404 A009405 A009406


KEYWORD

sign


AUTHOR

R. H. Hardin


EXTENSIONS

Extended with signs by Olivier Gérard, Mar 15 1997
Previous Mathematica program replaced by Harvey P. Dale, Aug 27 2013


STATUS

approved



