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A135082
Column 1 of triangle A135080.
8
1, 2, 7, 40, 326, 3492, 46558, 744320, 13889080, 296459376, 7125938790, 190502850972, 5607258255032, 180198503713952, 6278311585490032, 235730921392184452, 9489040823468191328, 407662178549724426176
OFFSET
0,2
COMMENTS
Triangle A135080 transforms diagonals in the table of coefficients of successive self-compositions of x+x^2 (cf. A122888).
PROG
(PARI) {a(n)=local(F=x, M, N, P); M=matrix(n+3, n+3, r, c, F=x; for(i=1, r+c-2, F=subst(F, x, x+x^2+x*O(x^(n+3)))); polcoeff(F, c)); N=matrix(n+2, n+2, r, c, M[r, c]); P=matrix(n+2, n+2, r, c, M[r+1, c]); (P~*N~^-1)[n+2, 2]}
CROSSREFS
Cf. A135080 (triangle); other columns: A135081, A135083.
Sequence in context: A166904 A105625 A367255 * A372348 A102317 A361828
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Nov 18 2007
STATUS
approved