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%I #9 Oct 13 2015 04:04:05
%S 6,9,12,14,18,21,24,27,28,30,36,42,45,46,48,49,54,56,60,63,66,69,70,
%T 72,78,81,84,86,90,92,94,96,98,99,102,105,108,112,114,117,120,126,129,
%U 132,134,135,138,140,141,144,145,147,150,153,154,156,161,162,166,168,171,172,174,180
%N Real positive integers with more than one distinct factorization in Z[sqrt(-5)].
%C To count as distinct from another factorization, a factorization must not be derived from the other by multiplication by units. For example, -2 * -3 is not distinct from 2 * 3 as a factorization of 6.
%C If a number is in this sequence, then so are all its real positive integer multiples. The negative multiples also have more than one factorization, but of course one has to remember to put in the -1 as needed.
%C Z[sqrt(-5)] has class number 2. This means that while a number may have more than one factorization, all factorizations have the same number of factors. If one factorization seems to have fewer factors, then it is an incomplete factorization.
%e 14 = 2 * 7 = (3 - sqrt(-5))(3 + sqrt(-5)), so 14 is in the sequence.
%Y Cf. A020669 (superset).
%K nonn
%O 1,1
%A _Alonso del Arte_, Oct 03 2015