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 A175861 #6 Nov 08 2018 21:12:56 %S A175861 0,0,0,0,0,0,0,1,1,0,0,0,0,1,1,0,0,0,0,0,0,0,0,1,1,0,0,0,0,0,0,1,1,0, %T A175861 0,0,0,1,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,0,0,0,0,0,0,1,1,0,0,0,0,0, %U A175861 0,0,0,0,0,1,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,1,0,0,0,0,1,1,0 %N A175861 a(n) = characteristic function of numbers k such that A175856(m) = k has no solution for any m, where A175856(m): a(m) = m for m = noncomposites, a(m) = previous term - 1 for m = composites. %C A175861 a(n) = characteristic function of numbers from A175859(n). a(n) = 1 if A175856(m) not equal to n for any m, else 0. a(n) = 1 for such n that A175862(n) = 0. a(n) = 0 for such n that A175862(n) >= 1. a(n) + A175860(n) = A000012(n). %H A175861 Antti Karttunen, <a href="/A175861/b175861.txt">Table of n, a(n) for n = 1..10000</a> %H A175861 <a href="/index/Ch#char_fns">Index entries for characteristic functions</a> %F A175861 a(n) = 1 - A175860(n). %o A175861 (PARI) A175861(n) = (1-A175860(n)); \\ Uses program from A175860. - _Antti Karttunen_, Nov 08 2018 %Y A175861 Cf. A175856, A175857, A175858, A175859, A175860, A175862. %K A175861 nonn %O A175861 1,1 %A A175861 _Jaroslav Krizek_, Sep 29 2010