OFFSET
0,3
LINKS
Jean-François Alcover, Table of n, a(n) for n = 0..80
N. J. A. Sloane, Transforms
FORMULA
a(n) = 1/(2*exp(1))*Sum_{r,s>=0} [r*s]^n/(2^r*s!), where [m]^n = m*(m+1)*...*(m+n-1) is the rising factorial.
MAPLE
read "transforms" ; A000670 := proc(n) local k ; if n = 0 then 1; else add(k!*combinat[stirling2](n, k), k=1..n) ; fi ; end: A000110 := proc(n) local k ; add(combinat[stirling2](n, k), k=0..n) ; end: A104600 := proc(n) local k ; add(combinat[stirling1](n, k)*A000670(k)*A000110(k), k=0..n) ; end: A121020 := proc(nmax) local a104600 ; a104600 := [seq(A104600(n), n=0..nmax)] ; LAH(a104600) ; end: A121020(20) ; # R. J. Mathar, Jan 21 2008
MATHEMATICA
a[n_] := a[n] = (1/(2 E)) Sum[Sum[Product[r s + k, {k, 0, n - 1}]/(2^r s!), {r, 0, Infinity}], {s, 0, Infinity}];
Reap[For[n = 0, n <= 80, n++, Print[n, " ", a[n]]; Sow[a[n]]]][[2, 1]] (* Jean-François Alcover, Apr 04 2020 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Vladeta Jovovic, Sep 08 2006, Sep 19 2006
EXTENSIONS
More terms from R. J. Mathar, Jan 21 2008
STATUS
approved