A009667 E.g.f. tan(sin(x))*x, even numbered terms only.

0, 2, 4, -18, -856, -10950, 502764, 42386918, 552455120, -212988964878, -23803145936300, 497029073217886, 554580759766596984, 68481112266792124458, -10157252026016020122820

Offset

0,2

Links

Robert Israel, Table of n, a(n) for n = 0..250

Formula

a(n) = 2*A024225(n). [Martin Ettl, Nov 08 2012]

a(n) = (2*n)!*[x^(2*n)] tan(sin(x))*x. - Robert Israel, Mar 11 2019

Maple

S:= series(x*tan(sin(x)), x, 61):
seq(n!*coeff(S, x, n), n=0..60, 2); # Robert Israel, Mar 11 2019

Mathematica

nn = 30; t = Range[0, nn]! CoefficientList[Series[Tan[Sin[x]]*x, {x, 0, nn}], x]; Take[t, {1, nn, 2}] (* T. D. Noe, Nov 08 2012 *)

Crossrefs

Cf. A024225.

Sequence in context: A306193 A323702 A318531 * A356123 A009508 A275000

Adjacent sequences: A009664 A009665 A009666 * A009668 A009669 A009670

Keyword

sign

Author

R. H. Hardin

Extensions

Extended with signs by Olivier Gérard, Mar 15 1997

Status

approved