A136224 Column 3 of triangle A136220; also equals column 0 of U^4 where U = A136228.

1, 4, 36, 442, 6742, 122350, 2571620, 61426282, 1643616044, 48708655760, 1583981114700, 56090062706944, 2148733943483128, 88554674908328872, 3907197406833303644, 183780036631720987407, 9180785177015520963631

Offset: 0

Author

Paul D. Hanna, Dec 25 2007

Keywords

• nonn

Comments

P = A136220 is a triangular matrix where column k of P^3 equals column 0 of P^(3k+3) such that column 0 of P^3 equals column 0 of P shift one place left.

Crossrefs

Cf. A136220 (P), A136228 (U); other columns of P: A136221, A136222, A136223.

Programs

PARI

{a(n)=local(P=Mat(1),U,PShR);if(n==0,1,for(i=0,n+2, PShR=matrix(#P,#P, r,c, if(r>=c,if(r==c,1,if(c==1,0,P[r-1,c-1]))));U=P*PShR^2; U=matrix(#P+1, #P+1, r,c, if(r>=c, if(r<#P+1,U[r,c], if(c==1,(P^3)[ #P,1],(P^(3*c-1))[r-c+1,1])))); P=matrix(#U, #U, r,c, if(r>=c, if(r<#U,P[r,c], (U^c)[r-c+1,1]))));P[n+4,4])}