

A009081


E.g.f. is cos(tan(x)/cos(x)), coefficients of even powers of x.


1



1, 1, 19, 517, 18023, 587529, 19183749, 12219870323, 3379214470193, 883981857320943, 238930492488456221, 66829754023676225259, 18410558239851140719561, 4167711609283156286652647, 82954815883633697917244747, 1284116651310135986426544039581
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OFFSET

0,3


COMMENTS

All coefficients of odd powers of x are zero.


LINKS



MATHEMATICA

With[{nn=30}, Take[CoefficientList[Series[Cos[Tan[x]/Cos[x]], {x, 0, nn}], x]Range[0, nn]!, {1, 1, 2}]] (* Harvey P. Dale, Jan 28 2012 *)


PROG

(PARI)
x='x+O('x^66); /* that many terms */
v=Vec(serlaplace(cos(tan(x)/cos(x))));
vector(#v\2, j, v[2*j1]) /* show terms */


CROSSREFS



KEYWORD

sign


AUTHOR



EXTENSIONS



STATUS

approved



