OFFSET
0,4
LINKS
Index entries for linear recurrences with constant coefficients, signature (1,1,1,-2,-2,3,-1,-1,-3,4,4,-3,-1,-1,3,-2,-2,1,1,1,-1).
E. Bannai, S. T. Dougherty, M. Harada and M. Oura, Type II Codes, Even Unimodular Lattices and Invariant Rings, IEEE Trans. Information Theory, Volume 45, Number 4, 1999, 1194-1205.
FORMULA
G.f.: (x^18 + 4*x^17 + 19*x^16 + 30*x^15 + 47*x^14 + 97*x^13 + 128*x^12 + 113*x^11 + 186*x^10 + 161*x^9 + 97*x^8 + 108*x^7 + 98*x^6 + 27*x^5 + 23*x^4 + 13*x^3 - x + 1)/((x - 1)^6*(x + 1)^3*(x^2 + x + 1)^4*(x^2 - x + 1)^2).
a(n) ~ 2*n^5/135. - Stefano Spezia, Aug 21 2022
MATHEMATICA
CoefficientList[Series[(x^18+4x^17+19x^16+30x^15+47x^14+97x^13+ 128x^12+ 113x^11+ 186x^10+161x^9+97x^8+108x^7+ 98x^6+27x^5+23x^4+13x^3-x+1)/ ((x-1)^6(x+1)^3(x^2+x+1)^4(x^2-x+1)^2), {x, 0, 40}], x] (* Harvey P. Dale, Jan 28 2015 *)
CROSSREFS
KEYWORD
nonn,easy,nice
AUTHOR
EXTENSIONS
More terms from Antonio G. Astudillo (afg_astudillo(AT)hotmail.com), Jun 15 2001
STATUS
approved