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A296835 Expansion of e.g.f. exp(x*tan(x/2)) (even powers only). 3
1, 1, 4, 33, 451, 9110, 253401, 9246881, 427272364, 24332740569, 1671761966755, 136185663849422, 12966840876896193, 1425738305622057713, 179172604156015950676, 25507107918052543195905, 4081610970381242583997171, 729135575105289450378655526 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Table of n, a(n) for n=0..17.

FORMULA

a(n) = (2*n)! * [x^(2*n)] exp(x*tan(x/2)).

EXAMPLE

exp(x*tan(x/2)) = 1 + x^2/2! + 4*x^4/4! + 33*x^6/6! + 451*x^8/8! + ...

MATHEMATICA

nmax = 17; Table[(CoefficientList[Series[Exp[x Tan[x/2]], {x, 0, 2 nmax}], x] Range[0, 2 nmax]!)[[n]], {n, 1, 2 nmax + 1, 2}]

CROSSREFS

Cf. A001469, A003723, A006229, A009252, A009273, A110501, A296836.

Sequence in context: A268293 A193421 A179421 * A002190 A101981 A002018

Adjacent sequences:  A296832 A296833 A296834 * A296836 A296837 A296838

KEYWORD

nonn

AUTHOR

Ilya Gutkovskiy, Dec 21 2017

STATUS

approved

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Last modified January 19 21:47 EST 2020. Contains 331066 sequences. (Running on oeis4.)