OFFSET
0,2
FORMULA
a(n) = exp(-1)*n!^2*F_2([n+1,n+1],[1,2] |1), F_2 the generalized hypergeometric function of type 2_F_2.
Let b_{n}(x) = Sum_{j>=0}(x*exp((j+n-1)!/(j-1)!-1)/j!) then a(n) = 2 [x^2] series b_{n}(x), where [x^2] denotes the coefficient of x^2 in the Taylor series for b_{n}(x).
MAPLE
MATHEMATICA
a[n_] := n!^2*HypergeometricPFQ[{n+1, n+1}, {1, 2}, 1.`40.]/E; Table[a[n] // Round, {n, 0, 14}] (* Jean-François Alcover, Jul 29 2013 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Peter Luschny, Mar 29 2011
STATUS
approved