A340080 a(n) = (1+A018804(n)) / gcd(n, 1+A018804(n)), where A018804(n) = Sum_{k=1..n} gcd(k, n).

2, 2, 2, 9, 2, 8, 2, 21, 22, 14, 2, 41, 2, 20, 46, 49, 2, 32, 2, 73, 22, 32, 2, 101, 66, 38, 82, 15, 2, 68, 2, 113, 106, 50, 118, 169, 2, 56, 42, 181, 2, 14, 2, 169, 38, 68, 2, 241, 134, 98, 166, 201, 2, 122, 38, 261, 62, 86, 2, 361, 2, 92, 274, 257, 226, 158, 2, 265, 226, 176, 2, 421, 2, 110, 326, 297, 274, 188

Offset: 1

Author

Antti Karttunen, Dec 31 2020

Keywords

• nonn

Links

• Antti Karttunen, Table of n, a(n) for n = 1..8191
• Antti Karttunen, Data supplement: n, a(n) computed for n = 1..65537

Crossrefs

Cf. A018804, A340078, A340079.

Programs

PARI

A018804(n) = sumdiv(n, d, n*eulerphi(d)/d); \\ From A018804
A340080(n) = { my(x=1+A018804(n)); x/gcd(n,x); };

Formula

a(n) = (1+A018804(n)) / gcd(n, 1+A018804(n)).