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 A110304 #12 Jan 14 2017 11:41:04 %S A110304 1,2,3,4,5,6,7,8,9,10,121,12,52,14,30,16,34,18,38,0,21,418,23,72,25, %T A110304 52,27,56,29,30,341,32,165,34,70,36,74,38,78,0,41,210,43,616,45,92,47, %U A110304 96,49,50,561,52,212,54,165,56,456,58,236,0,61,434,63,256,65,858,67,272,69 %N A110304 Least alternating multiple of alternators. %C A110304 An alternating integer is a positive integer for which, in base-10, the parity of its digits alternates. E.g., 121 is alternating because its consecutive digits are odd-even-odd, 1 being odd and 2 even. Of course, 1234567890 is also alternating. An alternator is a positive integer which has a multiple which is alternating. %C A110304 For n congruent to 0 mod 20, a(n) is shown as zero to indicate that n is not an alternator. %H A110304 45th International Mathematical Olympiad (45th IMO), <a href="http://www.jstor.org/stable/30044168">Problem #6 and Solution</a>, Mathematics Magazine, 2005, Vol. 78, No. 3, pp. 247, 250-251. %e A110304 a(11) = 121 because 121 is the least multiple of 11 which is alternating. %Y A110304 Cf. A030141, A110303, A110305. %K A110304 base,easy,nonn %O A110304 1,2 %A A110304 _Walter Nissen_, Jul 18 2005