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A187122
A diagonal of triangle A187120.
4
1, 9, 81, 855, 10758, 159633, 2750067, 54178485, 1204443432, 29871630837, 818490738402, 24571782872034, 802459134168208, 28332664539686670, 1075700621922471621, 43710289920461797346, 1893011243289589171122
OFFSET
3,2
COMMENTS
Definition of triangle: A187120(n,k) = [y^k] R_{n-1}(y+y^2) for k=3..n, n>3, where R_n(y) is the n-th row polynomial starting with R_3(y)=y^3.
FORMULA
Equals column 2 in the matrix cube of triangle A135080.
PROG
(PARI) {a(n)=local(Rn=y^3); for(m=3, n+1, Rn=subst(truncate(Rn), y, y+y^2+O(y^m))); polcoeff(Rn, n, y)}
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Mar 08 2011
STATUS
approved