A329609 Numbers k such that A156552(k) is a multiple of 3.

1, 4, 9, 10, 16, 21, 22, 25, 30, 34, 36, 39, 40, 46, 49, 55, 57, 62, 64, 66, 81, 82, 84, 85, 87, 88, 90, 91, 94, 100, 102, 105, 111, 115, 118, 120, 121, 129, 133, 134, 136, 138, 144, 146, 154, 155, 156, 159, 160, 166, 169, 183, 184, 186, 187, 189, 194, 195, 196, 198, 203, 205, 206, 213, 218, 220, 225, 228, 235, 237, 238, 246

Offset

1,2

Comments

Not a multiplicative semigroup. For example, although 10 and 21 are present, 210 is missing. Compare to A332820. - Antti Karttunen, Jan 17 2023

Links

Antti Karttunen, Table of n, a(n) for n = 1..20000

Prog

(PARI)
A156552(n) = {my(f = factor(n), p2 = 1, res = 0); for(i = 1, #f~, p = 1 << (primepi(f[i, 1]) - 1); res += (p * p2 * (2^(f[i, 2]) - 1)); p2 <<= f[i, 2]); res}; \\ From A156552
isA329609(n) = !(A156552(n)%3);

Crossrefs

Cf. A000290 (subsequence), A156552, A329603, A329604, A332812.

Positions of zeros in A329903, of nonzeros in A341353, of ones in A353269 (characteristic function), A353418 (Dirichlet inverse of char.fun), A359836.

Sequence A332449 sorted into ascending order.

Cf. also A353303, A353304 and A332820.

Sequence in context: A010406 A010451 A080064 * A340784 A260963 A243188

Adjacent sequences: A329606 A329607 A329608 * A329610 A329611 A329612

Keyword

nonn

Author

Antti Karttunen, Nov 21 2019

Status

approved