A009246 Expansion of exp(tan(x))/exp(x).

1, 0, 0, 2, 0, 16, 40, 272, 1792, 10176, 97536, 649472, 7185024, 59488768, 710474752, 7190574848, 91774959616, 1098412695552, 15045919272960, 206459812782080, 3050231036903424, 46832947884802048, 747964948517158912, 12622945785546997760

Offset

0,4

Links

Vincenzo Librandi, Table of n, a(n) for n = 0..200

Formula

E.g.f.: exp(tan(x))/exp(x).

E.g.f.: E(0)-1, where E(k) = 2 + (tan(x)-x)/(2*k + 1 - (tan(x)-x)/E(k+1) ); (continued fraction). - Sergei N. Gladkovskii, Dec 23 2013

Mathematica

Table[n!, {n, 0, 21}] * CoefficientList[Series[Exp[Tan[x]-x], {x, 0, 21}], x]

Crossrefs

Sequence in context: A015154 A346119 A009266 * A358629 A338448 A012414

Adjacent sequences: A009243 A009244 A009245 * A009247 A009248 A009249

Keyword

nonn,easy

Author

R. H. Hardin

Extensions

Extended and signs tested by Olivier Gérard, Mar 15 1997

Status

approved