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 A075424 #9 Dec 27 2023 13:09:16 %S A075424 0,1,0,1,4,5,0,1,2,9,4,5,12,13,0,1,4,5,2,9,20,21,4,1,4,1,12,13,28,29, %T A075424 0,1,32,33,4,5,36,37,2,9,40,41,20,13,14,45,4,5,2,9,4,25,4,5,12,13,56, %U A075424 57,28,29,60,9,0,1,64,65,32,33,68,69,4,5,72,13,36,37,76,77,2,1,2,81,40,41 %N A075424 a(n) = A075423(A075423(n)). %C A075424 From _Robert Israel_, Apr 11 2019: (Start) %C A075424 a(n) == n (mod 2). %C A075424 a(n) = 0 iff n is in A000079. %C A075424 a(n) = n-2 iff n-1 is in A007674. (End) %H A075424 Robert Israel, <a href="/A075424/b075424.txt">Table of n, a(n) for n = 2..10000</a> %p A075424 A075423:= n -> convert(numtheory:-factorset(n),`*`)-1: %p A075424 map(A075423@@2, [$2..100]); # _Robert Israel_, Apr 11 2019 %Y A075424 Cf. A000079, A007674, A075423, A075425. %K A075424 nonn,look %O A075424 2,5 %A A075424 _Reinhard Zumkeller_, Sep 15 2002