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 A109752 #14 Aug 06 2014 16:19:01 %S A109752 1,2,3,4,5,6,7,8,90 %N A109752 Using the lunar product (see A087062 for definition), numbers n such that if n divides a*b, then n must divide either a or b. The multiplicative identity, 9, is excluded by convention. %C A109752 This condition is one of the definitions of a prime, so these numbers could be called lunar primes (cf. A087097). %H A109752 D. Applegate, M. LeBrun and N. J. A. Sloane, <a href="http://arxiv.org/abs/1107.1130">Dismal Arithmetic</a> [Note: we have now changed the name from "dismal arithmetic" to "lunar arithmetic" - the old name was too depressing] %H A109752 <a href="/index/Di#dismal">Index entries for sequences related to dismal (or lunar) arithmetic</a> %e A109752 90 is a member because the lunar multiples of 90 are the same as the numbers ending with a 0 and if neither a nor b ends in 0, then neither does a*b. %Y A109752 Cf. A087062, A087097. %K A109752 base,fini,full,nonn,less %O A109752 1,2 %A A109752 _David Wasserman_, Aug 11 2005