A012748 - OEIS

A012748

Expansion of e.g.f. sec(arctanh(x)*cos(x)), only even powers.

1, 1, 1, 25, 3617, 340145, 40490657, 7034559753, 1668333374913, 504856533178465, 189500285350524865, 86696156445549770233, 47524548345395009982689, 30739504895562596416971025, 23162222253680333719652996449, 20112913566033287819336502367465, 19939158697176271310635403636418945

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

OFFSET

0,4

LINKS

Stefano Spezia, Table of n, a(n) for n = 0..150

EXAMPLE

E.g.f. = 1 + x^2/2! + x^4/4! + 25*x^6/6! + 3617*x^8/8! + ...

MATHEMATICA

nmax=32; DeleteCases[CoefficientList[Series[Sec[ArcTanh[x]Cos[x]], {x, 0, nmax}], x], 0](2Range[0, nmax/2])! (* Stefano Spezia, Jun 21 2024 *)

CROSSREFS

Sequence in context: A373878 A185826 A178026 * A337725 A036512 A306380

Adjacent sequences: A012745 A012746 A012747 * A012749 A012750 A012751