A009530 Expansion of e.g.f. sin(tanh(x)/cos(x)).

1, 0, 12, -336, -2096, -1043328, -29488704, -8894706432, -389860902656, -170568226222080, -6327905330549760, -6080018829202427904, 242897035394043301888, -323994054628796940582912, 123697309877515731773669376, -13142696592417683099946516480

Offset: 0

Author

R. H. Hardin

Keywords

• sign

Comments

Among solutions to a(n)=2n are primes, twice primes (A001747) and also further numbers.

Programs

Mathematica

Sin[ Tanh[ x ]/Cos[ x ] ] (* Odd Part *)

PARI

x='x+O('x^34); v = Vec(serlaplace(sin(tanh(x)/cos(x)))); vector(#v\2, n, v[2*n-1]) \\ Michel Marcus, Apr 02 2017

Extensions

Extended with signs by Olivier Gérard, Mar 15 1997