OFFSET
0,2
COMMENTS
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..249
FORMULA
a(n) = denominator((-1)^n * Sum_{m=0..2*n} 2^m * (Sum_{k=0..m} k! * Stirling2(m,k) * Stirling1(m+k,m) / (m+k)!) * binomial(2*n,m)).
MATHEMATICA
Denominator[With[{nn = 50}, Table[(CoefficientList[Series[x/((x^2 + 1)*ArcTan[x]), {x, 0, 2*nn}], x])[[n]], {n, 1, 2*nn + 1, 2}]]] (* G. C. Greubel, Apr 12 2017 *)
PROG
(PARI) x='x+O('x^66); v=Vec(x/((x^2+1)*atan(x))); vector(#v\2, n, denominator(v[2*n-1])) \\ Joerg Arndt, Apr 30 2013
(PARI) a(n) = denominator((-1)^n*sum(l=0, 2*n, 2^l * (sum(k=0, l, (k!*stirling(l, k, 2) * stirling(l+k, l, 1)) / (l+k)!)) * binomial(2*n, l))); \\ Michel Marcus, Apr 30 2013
CROSSREFS
KEYWORD
nonn,frac
AUTHOR
Michel Marcus, Apr 30 2013
STATUS
approved