OFFSET
0,3
LINKS
Vladimir Kruchinin, Composition of ordinary generating functions, arXiv:1009.2565 [math.CO], 2010.
Index entries for linear recurrences with constant coefficients, signature (1,2,3,4,3,1)
FORMULA
a(n+1) = sum(m=1..n, sum(k=m..n, binomial(k,n-k) *sum(j=0..m, binomial(m,j) *binomial(j,k-3*m+2*j)))).
MATHEMATICA
CoefficientList[Series[1/(1-x^6-3x^5-4x^4-3x^3-2x^2-x), {x, 0, 30}], x] (* or *) LinearRecurrence[{1, 2, 3, 4, 3, 1}, {1, 1, 3, 8, 21, 53}, 30] (* Harvey P. Dale, Aug 30 2014 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Vladimir Kruchinin, Feb 28 2011
EXTENSIONS
More terms from Harvey P. Dale, Aug 30 2014
STATUS
approved