OFFSET
0,2
COMMENTS
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..300
MATHEMATICA
T[n_, k_] := T[n, k] = If[k < 0 || n < k, 0, If[n == 0 && k == 0, 1, If[k == 0, T[n - 1, n - 1], T[n, k - 1] + n*T[n - 1, k - 1]]]]; Table[Sum[T[n, k], {k, 0, n}], {n, 0, 30}] (* G. C. Greubel, Dec 15 2017 *)
PROG
(PARI) { T(n, k)=if(k<0 || n<k, 0, if(n==0 && k==0, 1, if(k==0, T(n-1, n-1), T(n, k-1)+n*T(n-1, k-1)))) }; for(n=0, 20, print1(sum(k=0, n, T(n, k)), ", ")) \\ G. C. Greubel, Dec 15 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Aug 07 2007
STATUS
approved