OFFSET
0,4
COMMENTS
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..445
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], n*T[n - 1, k - 1] + T[n - 1, k - 2]]]]; Table[T[n, 0], {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), n*T(n-1, k-1)+T(n-1, k-2)))) }; for(n=0, 30, print1(T(n, 0), ", ")) \\ G. C. Greubel, Dec 15 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Aug 07 2007
STATUS
approved