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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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified September 28 01:20 EDT 2020. Contains 337388 sequences. (Running on oeis4.)