OFFSET
20,2
LINKS
Alois P. Heinz, Table of n, a(n) for n = 20..1000
FORMULA
Conjectures from Chai Wah Wu, Apr 18 2024: (Start)
a(n) = a(n-1) + a(n-2) - a(n-5) - a(n-6) - a(n-7) + a(n-8) + a(n-9) + a(n-10) - a(n-13) - a(n-14) + a(n-15) for n > 40.
G.f.: x^20*(-x^20 + 2*x^16 + 2*x^15 + 4*x^14 + x^13 - 3*x^12 - 7*x^11 - 9*x^10 - 5*x^9 + 2*x^8 + 8*x^7 + 9*x^6 + 8*x^5 + x^4 - 3*x^3 - 5*x^2 - 4*x - 1)/((x - 1)^5*(x + 1)^2*(x^2 + 1)*(x^2 + x + 1)*(x^4 + x^3 + x^2 + x + 1)). (End)
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Jun 23 2014
STATUS
approved