A340078 a(n) = gcd(n, 1+A018804(n)), where A018804(n) = Sum_{k=1..n} gcd(k, n).

1, 2, 3, 1, 5, 2, 7, 1, 1, 2, 11, 1, 13, 2, 1, 1, 17, 2, 19, 1, 3, 2, 23, 1, 1, 2, 1, 7, 29, 2, 31, 1, 1, 2, 1, 1, 37, 2, 3, 1, 41, 14, 43, 1, 5, 2, 47, 1, 1, 2, 1, 1, 53, 2, 5, 1, 3, 2, 59, 1, 61, 2, 1, 1, 1, 2, 67, 1, 1, 2, 71, 1, 73, 2, 1, 1, 1, 2, 79, 1, 1, 2, 83, 1, 1, 2, 1, 1, 89, 2, 1, 1, 3, 2, 1, 3, 97, 2

Offset: 1

Author

Antti Karttunen, Dec 30 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, A340079, A340080.

Cf. also A055023, A323071 (similar but different sequences).

Programs

PARI

A018804(n) = sumdiv(n, d, n*eulerphi(d)/d); \\ From A018804
A340078(n) = gcd(n,1+A018804(n));

Formula

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