OFFSET
0,3
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..2495
Vladimir Kruchinin, Composition of ordinary generating functions, arXiv:1009.2565 [math.CO], 2010.
Index entries for linear recurrences with constant coefficients, signature (1,2,3,3,2,1).
FORMULA
a(n):=sum(m=1..n, sum(k=m..n, binomial(m,k-m)*sum(j=0..k, binomial(k,j)*binomial(j,n-3*k+2*j)))), a(0)=1.
MAPLE
seq(coeff(series(1/(1-x-2*x^2-3*x^3-3*x^4-2*x^5-x^6), x, n+1), x, n), n = 0 .. 30); # Muniru A Asiru, Feb 24 2019
MATHEMATICA
CoefficientList[Series[1/(1-x-2x^2-3x^3-3x^4-2x^5-x^6), {x, 0, 30}], x] (* or *) LinearRecurrence[ {1, 2, 3, 3, 2, 1}, {1, 1, 3, 8, 20, 50}, 40] (* Harvey P. Dale, Jul 21 2024 *)
PROG
(Maxima) a(n):=sum(sum(binomial(m, k-m)*sum(binomial(k, j)*binomial(j, n-3*k+2*j), j, 0, k), k, m, n), m, 1, n);
(PARI) Vec(1/(1-x-2*x^2-3*x^3-3*x^4-2*x^5-x^6)+O(x^44)) \\ Joerg Arndt, Mar 04 2011
CROSSREFS
KEYWORD
nonn,changed
AUTHOR
Vladimir Kruchinin, Mar 01 2011
STATUS
approved