OFFSET
1,2
FORMULA
a(n) = Sum_{k=1..n} binomial(k+3,4) * (floor(n/k) mod 2).
G.f.: -1/(1-x) * Sum_{k>=1} (-x)^k/(1-x^k)^5 = 1/(1-x) * Sum_{k>=1} binomial(k+3,4) * x^k/(1+x^k).
PROG
(PARI) a(n) = sum(k=1, n, (-1)^(k-1)*binomial(n\k+4, 5));
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Oct 24 2023
STATUS
approved