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 A121274 #10 Apr 09 2014 10:15:52 %S A121274 1,2,5,4,13,6,13,14,9,10,31,17,29,14,33,16,49,18,47,23,21,22,67,24,25, %T A121274 36,67,37,107,30,61,55,33,34,55,36,77,38,79,65,143,53,93,58,45,61,139, %U A121274 57,77,76,127,80,157,65,113,85,57,72,221,60,125,62,63,64,100,79,141,81 %N A121274 a(n) = n-th integer from among those positive integers which are coprime to (n-th integer from among those positive integers which are coprime to n). %e A121274 6 is the 5th positive integer which is coprime to 5. (1,2,3,4,6,7,8.... is the sequence of positive integers which are coprime to 5 and 6 is the 5th such integer.) 1,5,7,11,13,17,19,... are the positive integers which are coprime to 6. 13 is the 5th of these integers, so a(5) = 13. %Y A121274 Cf. A069213. %K A121274 nonn %O A121274 1,2 %A A121274 _Leroy Quet_, Aug 23 2006 %E A121274 Extended by _Ray Chandler_, Aug 29 2006