OFFSET
1,2
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..1000
FORMULA
G.f. A(x) satisfies A(x) = x/(1 - 7*x) + A(x^7).
If n == 0 (mod 7), a(n) = 7^n + a(n/7) otherwise a(n) = 7^n.
a(n) = Sum_{d|n} d * A373277(d).
PROG
(PARI) b(n, k) = sumdiv(n, d, (gcd(d, k)==1)*(moebius(d)*k^(n/d)))/(k*n);
a(n, k=7) = sumdiv(n, d, d*b(d, k));
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, May 30 2024
STATUS
approved