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 A121215 #9 Apr 09 2014 10:15:52 %S A121215 1,4,9,10,30,14,56,22,33,24,143,27,182,35,48,44,289,40,361,50,70,62, %T A121215 529,57,155,72,105,76,841,64,1023,96,114,94,140,84,1369,110,132,100, %U A121215 1681,90,1849,124,144,136,2256,112,406,128,180,154,2809,126,270,158,204,176 %N A121215 a(1)=1. a(n) = n-th integer from among those positive integers which do not occur earlier in the sequence and which are not coprime to n. %e A121215 2,3,6,8,12,14,15,16,...is the sequence of positive integers which do not occur among the first 5 terms of the sequence and which are not coprime to 6. 14 is the 6th of these integers, so a(6) = 14. %Y A121215 Cf. A105054. %K A121215 nonn %O A121215 1,2 %A A121215 _Leroy Quet_, Aug 20 2006 %E A121215 Extended by _Ray Chandler_, Aug 22 2006