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 A253898 #4 Jan 25 2015 21:48:58 %S A253898 1,2,7,11,13,17,19,23,25,26,27,29,31,32,34,37,38,41,42,43,46,47,49,51, %T A253898 52,53,54,57,58,59,61,62,64,65,67,68,69,71,73,74,76,79,81,82,83,85,86, %U A253898 87,89,92,93,94,95,96,97,98,100,101,103,106,107,109,110,111,113,114,115,116,118,119 %N A253898 Complement of A253897. %C A253898 Numbers n such that the sequence A127644 with a(1) = n does not give a permutation of the natural numbers. See A127644 for more information. %o A253898 (PARI) b(r)=v=[r];n=1;while(n<100,p=prod(i=1,#v,v[i]);if(p*n\(vecsum(v)+n)==p*n/(vecsum(v)+n)&&!vecsearch(vecsort(v),n),v=concat(v,n);n=0);n++);#v %o A253898 r=1;while(r<100,if(b(r)<50,print1(r,", "));r++) %Y A253898 Cf. A127644, A253897. %K A253898 nonn %O A253898 1,2 %A A253898 _Derek Orr_, Jan 17 2015