A135883 Column 2 of triangle A135880.

1, 3, 15, 99, 814, 8057, 93627, 1252752, 19003467, 322722064, 6071897378, 125464556309, 2826120900315, 68954181763586, 1812280504183309, 51059994255961903, 1535575877864707548, 49107734497585814006

Offset

0,2

Links

Table of n, a(n) for n=0..17.

Example

Equals column 2 of triangle P=A135880:
1;
1, 1;
2, 2, 1;
6, 7, 3, 1;
25, 34, 15, 4, 1;
138, 215, 99, 26, 5, 1;
970, 1698, 814, 216, 40, 6, 1;
8390, 16220, 8057, 2171, 400, 57, 7, 1; ...
where column k of P^2 equals column 0 of P^(2k+2)
such that column 0 of P^2 equals column 0 of P shift left.

Prog

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

Crossrefs

Cf. A135880; other columns: A135881, A135882, A135884.

Sequence in context: A361596 A255806 A226515 * A372157 A147664 A219779

Adjacent sequences: A135880 A135881 A135882 * A135884 A135885 A135886

Keyword

nonn

Author

Paul D. Hanna, Dec 15 2007

Status

approved