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A009530 Expansion of e.g.f. sin(tanh(x)/cos(x)). 2

%I

%S 1,0,12,-336,-2096,-1043328,-29488704,-8894706432,-389860902656,

%T -170568226222080,-6327905330549760,-6080018829202427904,

%U 242897035394043301888,-323994054628796940582912,123697309877515731773669376,-13142696592417683099946516480

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

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

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

%o (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

%K sign

%O 0,3

%A _R. H. Hardin_

%E Extended with signs by _Olivier GĂ©rard_, Mar 15 1997

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Last modified November 15 11:18 EST 2019. Contains 329144 sequences. (Running on oeis4.)