A374475 Numbers k such that the least prime dividing the sum of divisors of k is equal to the least prime not dividing k.

2, 3, 5, 7, 8, 11, 13, 15, 17, 19, 21, 23, 27, 29, 31, 32, 33, 35, 37, 39, 41, 43, 45, 47, 50, 51, 53, 55, 57, 59, 61, 63, 65, 67, 69, 71, 73, 75, 77, 79, 83, 85, 87, 89, 91, 93, 95, 97, 98, 99, 101, 103, 105, 107, 109, 111, 113, 115, 117, 119, 123, 125, 127, 128, 129, 131, 133, 135, 137, 139, 141, 143, 145, 147

Offset: 1

Author

Antti Karttunen, Aug 06 2024

Keywords

• nonn

Links

• Antti Karttunen, Table of n, a(n) for n = 1..12000

Crossrefs

Cf. A000203, A020639, A053669, A374474 (characteristic function), A374476 (composite terms).

Cf. also A370125.

Programs

PARI

A020639(n) = if(1==n,n,vecmin(factor(n)[, 1]));
A053669(n) = forprime(p=2, , if(n%p, return(p))); \\ From A053669
A374474(n) = (A020639(sigma(n))==A053669(n));
isA374475 = A374474;