This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A262828 #9 Oct 13 2015 04:04:05 %S A262828 6,9,12,14,18,21,24,27,28,30,36,42,45,46,48,49,54,56,60,63,66,69,70, %T A262828 72,78,81,84,86,90,92,94,96,98,99,102,105,108,112,114,117,120,126,129, %U A262828 132,134,135,138,140,141,144,145,147,150,153,154,156,161,162,166,168,171,172,174,180 %N A262828 Real positive integers with more than one distinct factorization in Z[sqrt(-5)]. %C A262828 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 A262828 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 A262828 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 A262828 14 = 2 * 7 = (3 - sqrt(-5))(3 + sqrt(-5)), so 14 is in the sequence. %Y A262828 Cf. A020669 (superset). %K A262828 nonn %O A262828 1,1 %A A262828 _Alonso del Arte_, Oct 03 2015