A129102 Column 2 of triangle A129100; also equals column 0 of matrix power A129100^4.

1, 4, 20, 136, 1360, 21204, 537748, 22891448, 1675538928, 214841466180, 48966357498452, 20069542925092392, 14932742187505262032, 20328765555338724571508, 50972424276515393704138196

Offset: 0

Author

Paul D. Hanna, Mar 29 2007

Keywords

• nonn

Crossrefs

Cf. A129100 (triangle); A129092 (column 0), A129101 (column 1), A129103 (column 3).

Programs

PARI

a(n)=local(A=Mat(1),B);for(m=1,n+3,B=matrix(m,m);for(r=1,m,for(c=1,r, if(r==c || r==1 || r==2,B[r,c]=1,if(c==1,B[r,1]=sum(i=1,r-1,A[r-1,i]), B[r,c]=(A^(2^(c-1)))[r-c+1,1])); )); A=B); return(A[n+3,3])