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 A242400 #5 Jul 05 2014 13:08:09 %S A242400 0,0,0,0,0,9,0,9,9,0,0,0,0,0,9,27,36,36,0,0,0,27,27,36,27,36,36,0,0,0, %T A242400 0,0,9,0,9,9,0,0,0,0,0,9,27,36,36,81,81,81,108,108,117,108,117,117,0, %U A242400 0,0,0,0,9,0,9,9,81,81,81,81,81,90,108,117,117,81 %N A242400 Differences between A008586 (multiples of 4) and A242399. %C A242400 a(n) = A008586(n) - A242399(n); %C A242400 a(m) = 0 iff m is a term of A242407; %C A242400 a(A242407(n)) = 0; a(A242408(n)) > 0. %H A242400 Reinhard Zumkeller, <a href="/A242400/b242400.txt">Table of n, a(n) for n = 0..10000</a> %o A242400 (Haskell) %o A242400 a242400 n = a008586 n - a242399 n %Y A242400 Cf. A048728. %K A242400 nonn %O A242400 0,6 %A A242400 _Reinhard Zumkeller_, May 13 2014