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URL: https://oeis.org/A009530

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A009530
Expansion of e.g.f. sin(tanh(x)/cos(x)).
2
1, 0, 12, -336, -2096, -1043328, -29488704, -8894706432, -389860902656, -170568226222080, -6327905330549760, -6080018829202427904, 242897035394043301888, -323994054628796940582912, 123697309877515731773669376, -13142696592417683099946516480
OFFSET
0,3
COMMENTS
Among solutions to a(n)=2n are primes, twice primes (A001747) and also further numbers.
MATHEMATICA
Sin[ Tanh[ x ]/Cos[ x ] ] (* Odd Part *)
PROG
(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
CROSSREFS
Sequence in context: A110101 A185247 A368771 * A159363 A009680 A218820
KEYWORD
sign
AUTHOR
EXTENSIONS
Extended with signs by Olivier Gérard, Mar 15 1997
STATUS
approved