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

1,2

Links

Antti Karttunen, Table of n, a(n) for n = 1..8191

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

Formula

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

Prog

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

Crossrefs

Cf. A018804, A340079, A340080.

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

Sequence in context: A021816 A055023 A323071 * A126773 A353274 A326691

Adjacent sequences: A340075 A340076 A340077 * A340079 A340080 A340081

Keyword

nonn

Author

Antti Karttunen, Dec 30 2020

Status

approved