OFFSET
1,15
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..10000
PROG
(PARI) my(N=110, x='x+O('x^N)); Vec(sum(k=1, N, x^k*(1-x^k)/(1-x^(7*k))))
(PARI) a(n) = sumdiv(n, d, (d%7==1)-(d%7==2));
CROSSREFS
KEYWORD
sign,easy
AUTHOR
Seiichi Manyama, Jun 01 2024
STATUS
approved