A373385 Numbers k for which A059975(k) is a multiple of 3, where A059975 is fully additive with a(p) = p-1.

1, 6, 7, 8, 13, 15, 19, 20, 27, 31, 33, 36, 37, 42, 43, 44, 48, 49, 50, 51, 56, 61, 64, 67, 68, 69, 73, 78, 79, 87, 90, 91, 92, 97, 103, 104, 105, 109, 110, 114, 116, 120, 123, 125, 127, 133, 139, 140, 141, 151, 152, 157, 159, 160, 162, 163, 164, 169, 170, 177, 181, 186, 188, 189, 193, 195, 198, 199, 211, 212, 213

Offset: 1

Author

Antti Karttunen, Jun 06 2024

Keywords

• nonn

Comments

A multiplicative semigroup: if m and n are in the sequence, then so is m*n.

Links

• Antti Karttunen, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A059975.

Subsequences that are formed by intersecting this sequence with other multiplicative semigroups: A373384, A373473, A373492, A373494.

Cf. also A289142.

Programs

PARI

A059975(n) = {my(f = factor(n)); sum(i = 1, #f~, f[i, 2]*(f[i, 1] - 1)); };
isA373385(n) = !(A059975(n)%3);