A057950 Numbers primitive with respect to having more than one factorization into S-primes. See related sequences for definition.

441, 693, 1089, 1197, 1449, 1617, 1881, 1953, 2277, 2541, 2709, 2793, 2961, 3069, 3249, 3381, 3717, 3933, 4221, 4257, 4389, 4473, 4557, 4653, 4761, 4977, 5229, 5301, 5313, 5841, 5929, 6321, 6417, 6489, 6633, 6741, 6897, 6909, 7029, 7161, 7353, 7581

Offset: 1

Author

Jud McCranie, Oct 14 2000

Keywords

• nonn

Comments

A subset of A057949, removing terms that are a multiple of a smaller term.

Cubefree numbers with exactly 4 prime factors, all congruent to 3 mod 4. - Charlie Neder, Nov 26 2018

Examples

			441 is in S = {1, 5, 9, ... 4i+1, ...}, 441 = 9*49 = 21^2, 9, 21 and 49 as S-primes (A057948). 441 is primitive because it is not divisible by any smaller numbers with more than 1 factorization into S-primes. Multiples of 441 within S are not primitive.
		

Links

• Eric M. Schmidt, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A054520, A057948, A057949.

Cf. A004709 (cubefree numbers).

Extensions

Definition edited and offset corrected by Eric M. Schmidt, Dec 11 2016