A012553 Expansion of e.g.f. sech(sinh(x)*tan(x)) (only even powers).

1, 0, -12, -360, -4592, 866880, 144205248, 10276506240, -1972062209792, -1066588240250880, -219129099375885312, 33054966279836497920, 54554661987210721497088, 24677742880461438548951040, -913139288279696534090760192, -11701348914064333212059704197120, -10172088170748676628118741778890752

Offset

0,3

Links

Table of n, a(n) for n=0..16.

Example

E.g.f. = 1 - 12/4!*x^4 - 360/6!*x^6 - 4592/8!*x^8...

Mathematica

a[n_]:=(2n)!SeriesCoefficient[Sech[Sinh[x]*Tan[x]], {x, 0, 2n}]; Array[a, 17, 0] (* Stefano Spezia, Sep 16 2025 *)

Crossrefs

Sequence in context: A053068 A046969 A074094 * A128043 A012431 A012386

Adjacent sequences: A012550 A012551 A012552 * A012554 A012555 A012556

Keyword

sign

Author

Patrick Demichel

Extensions

a(14)-a(16) from Stefano Spezia, Sep 16 2025

Status

approved