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A296842 Expansion of e.g.f. cos(x*tan(x/2)) (even powers only). 9
1, 0, -3, -15, -14, 1755, 60357, 1740284, 45816165, 776485557, -37342503290, -7203185712261, -822818831400759, -85463040449605000, -8640073895507612019, -843669753827174738535, -73050419139737972150438, -3478007209663880122501701 (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)] cos(x*tan(x/2)).

EXAMPLE

cos(x*tan(x/2)) = 1 - 3*x^4/4! - 15*x^6/6! - 14*x^8/8! + 1755*x^10/10! + 60357*x^12/12! + ...

MATHEMATICA

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

CROSSREFS

Cf. A001469, A003710, A009080, A110501, A296839, A296841.

Sequence in context: A099476 A063628 A280201 * A279925 A279534 A181404

Adjacent sequences:  A296839 A296840 A296841 * A296843 A296844 A296845

KEYWORD

sign

AUTHOR

Ilya Gutkovskiy, Dec 21 2017

STATUS

approved

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Last modified October 19 04:40 EDT 2019. Contains 328211 sequences. (Running on oeis4.)