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 A073894 #4 Dec 05 2013 19:55:32 %S A073894 1,0,2,4,5,6,9,12,15,10,11,24,25,8,30,40,41,18,28,20,27,46,31,52,50, %T A073894 32,38,60,61,80,55,36,44,120,45,48,78,26,64,160,93,14,23,140,95,98,21, %U A073894 76,51,100,56,92,84,34,85,68,3,62,115,180,81,74,88,128,75,58,72,124,134 %N A073894 a(0)=1; a(n) for n > 0 is the smallest number not used earlier such that the concatenation of a(0),...,a(n) is a multiple of n+1. %C A073894 Does every nonnegative integer eventually appear? %e A073894 Concatenation of a(0),...,a(6) is 1024569, not used so far are 3, 7, 8, 10, 11, 12, ..., the smallest of these that appended to 1024569 gives a multiple of 8 is 12: 102456912 = 8*12807114, hence a(7) = 12. %Y A073894 Cf. A100769, A099552, A051883, A073893. %K A073894 base,nonn %O A073894 0,3 %A A073894 _Amarnath Murthy_, Aug 17 2002 %E A073894 Edited and extended by _Klaus Brockhaus_, Mar 28 2006