A326328 a(n) = (2*n)! [x^(2*n)] cosh(x)^(-3).

1, -3, 33, -723, 25953, -1376643, 101031873, -9795436563, 1212135593793, -186388033956483, 34859622790687713, -7791941518975112403, 2051293521728340489633, -628173356956461494680323, 221398076445213367209575553, -88980467736394156270609236243, 40450409313733718675802456121473

Offset: 0

Author

Peter Luschny, Jul 07 2019

Keywords

• sign

Comments

Apparently all terms except the initial 1 have 3-valuation 1. - F. Chapoton, Nov 25 2021

Crossrefs

Row 3 of A326327.

Programs

Maple

egf := cosh(z)^(-3): ser := series(egf, z, 36):
seq((2*n)!*coeff(ser, z, 2*n), n=0..16);