A009008 Expansion of e.g.f.: 1/cos(sin(x)) (even-indexed coefficients only).

1, 1, 1, -23, -415, 849, 421089, 16027897, -602344127, -137830187103, -6375572516543, 1282077224074761, 294398207479497377, 6767832711454751473, -10535904130516747834591, -2468712006908963695579879, 172926818125145929773139073

Offset

0,4

Links

Alois P. Heinz, Table of n, a(n) for n = 0..100 (first 51 terms from Vincenzo Librandi)

Mathematica

f[x_] := Sec@Sin[x]; Table[Derivative[2*n][f][0], {n, 0, 16}] (* Arkadiusz Wesolowski, Aug 18 2012 *)
With[{nmax = 50}, CoefficientList[Series[1/(Cos[Sin[x]]), {x, 0, nmax}], x]*Range[0, nmax]!][[1 ;; -1 ;; 2]] (* G. C. Greubel, Jul 21 2018 *)

Prog

(PARI) x='x+O('x^50); v=Vec(serlaplace(1/cos(sin(x)))); vector(#v\2, n, v[2*n-1]) \\ G. C. Greubel, Jul 21 2018

Crossrefs

Sequence in context: A245805 A016197 A199821 * A286787 A226847 A203147

Adjacent sequences: A009005 A009006 A009007 * A009009 A009010 A009011

Keyword

sign

Author

R. H. Hardin, Simon Plouffe

Extensions

a(16) from Arkadiusz Wesolowski, Aug 18 2012

Status

approved