A054092 T(n,n), array T as in A054090.

1, 1, 1, 3, 7, 25, 105, 547, 3367, 24033, 195169, 1777651, 17950551, 199059673, 2405063017, 31448531955, 442501797655, 6666753146497, 107081325959937, 1826636018849443, 32980276187719399, 628351055737088601

Offset: 0

Author

Clark Kimberling

Keywords

• nonn

Programs

PARI

{a(n)= local(A); if(n<3, n>=0, A=vector(n, i, 1); for(k=1, n-2, A[k+2]=(k-1)*A[k+1]+ k*A[k]+ 2); A[n])} /* Michael Somos, Nov 19 2006 */