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A374475
Numbers k such that the least prime dividing the sum of divisors of k is equal to the least prime not dividing k.
3
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
1,1
LINKS
PROG
(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;
CROSSREFS
Cf. A000203, A020639, A053669, A374474 (characteristic function), A374476 (composite terms).
Cf. also A370125.
Sequence in context: A112929 A242324 A099519 * A014121 A287893 A051600
KEYWORD
nonn
AUTHOR
Antti Karttunen, Aug 06 2024
STATUS
approved