A336924 a(n) = spf(1+sigma(n)), where spf is the smallest prime factor and sigma is the sum of divisors function.

2, 2, 5, 2, 7, 13, 3, 2, 2, 19, 13, 29, 3, 5, 5, 2, 19, 2, 3, 43, 3, 37, 5, 61, 2, 43, 41, 3, 31, 73, 3, 2, 7, 5, 7, 2, 3, 61, 3, 7, 43, 97, 3, 5, 79, 73, 7, 5, 2, 2, 73, 3, 5, 11, 73, 11, 3, 7, 61, 13, 3, 97, 3, 2, 5, 5, 3, 127, 97, 5, 73, 2, 3, 5, 5, 3, 97, 13, 3, 11, 2, 127, 5, 3, 109, 7, 11, 181, 7, 5, 113, 13

Offset: 1

Author

Antti Karttunen, Aug 09 2020

Keywords

• nonn

Links

• Antti Karttunen, Table of n, a(n) for n = 1..65537
• Index entries for sequences related to sigma(n)

Crossrefs

Cf. A000203, A020639, A071189, A088580.

Cf. also A336691, A336692, A336693, A336694, A336695, A336696.

Programs

PARI

A336924(n) = (factor((1+sigma(n)))[1, 1]);

Formula

a(n) = A020639(1+A000203(n)) = A020639(A088580(n)).