A373246 Greatest common divisor of n and its prime shadow: a(n) = gcd(n, A181819(n)).

1, 2, 1, 1, 1, 2, 1, 1, 3, 2, 1, 6, 1, 2, 1, 1, 1, 6, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 1, 1, 2, 1, 9, 1, 2, 1, 10, 1, 2, 1, 2, 3, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 12, 1, 2, 3, 1, 1, 2, 1, 2, 1, 2, 1, 3, 1, 2, 3, 2, 1, 2, 1, 2, 1, 2, 1, 12, 1, 2, 1, 2, 1, 6, 1, 2, 1, 2, 1, 2, 1, 2, 3, 1, 1, 2, 1, 2, 1

Offset: 1

Author

Antti Karttunen, May 29 2024

Keywords

• nonn

Links

• Antti Karttunen, Table of n, a(n) for n = 1..65537

Crossrefs

Cf. A181819, A373247, A373249.

Cf. A325755 [numbers k for which a(k) = A181819(k)], A353566 (their characteristic function).

Programs

PARI

A181819(n) = factorback(apply(e->prime(e),(factor(n)[,2])));
A373246(n) = gcd(n, A181819(n));

Formula

a(n) = gcd(A181819(n), A373247(n)).

a(n) = A181819(n) / A373249(n).