OFFSET
0,5
COMMENTS
Bill Gosper points out that this is a better fingerprint for the series than A309205.
MATHEMATICA
F[n_] := Module[{p}, p = 1 + O[x]; For[k=2, k <= n, k++, p = Cos[x p]]; p];
seq[n_] := Module[{v}, v = CoefficientList[F[n], x]; Table[(2(k - 1))!/ Denominator[v[[2k - 1]]], {k, 1, n}]];
seq[71] (* Jean-François Alcover, Aug 27 2019, from PARI *)
PROG
(PARI) \\ here F(n) gives n terms of power series.
F(n)={my(p=1+O(x)); for(k=2, n, p=cos(x*p)); p}
seq(n)={my(v=Vec(F(n))); vector(n, k, (2*(k-1))!/denominator(v[2*k-1]))} \\ Andrew Howroyd, Aug 17 2019
CROSSREFS
KEYWORD
nonn,frac
AUTHOR
N. J. A. Sloane, Jul 28 2019, following a suggestion from Bill Gosper.
EXTENSIONS
Terms a(31) and beyond from Andrew Howroyd, Aug 17 2019
STATUS
approved