A136224 - OEIS

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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

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OFFSET

0,2

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.

LINKS

Table of n, a(n) for n=0..16.

PROG

(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])}

CROSSREFS

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

Sequence in context: A052700 A167540 A374857 * A321963 A307903 A213596

Adjacent sequences: A136221 A136222 A136223 * A136225 A136226 A136227

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Dec 25 2007

STATUS

approved