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A057950
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Numbers primitive with respect to having more than one factorization into S-primes. See related sequences for definition.
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7
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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
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OFFSET
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1,1
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COMMENTS
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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
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LINKS
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EXAMPLE
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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.
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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