0,2

Triangle A135080 transforms diagonals in the table of coefficients of successive self-compositions of x+x^2 (cf. A122888).

(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]}

Cf. A135080 (triangle); other columns: A135081, A135083.

Adjacent sequences: A135079 A135080 A135081 this_sequence A135083 A135084 A135085

Sequence in context: A069732 A093985 A105625 this_sequence A102317 A031973 A132785

nonn

Paul D. Hanna (pauldhanna(AT)juno.com), Nov 18 2007