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 A278521 #6 Nov 29 2016 22:40:07 %S A278521 0,2,2,0,2,3,0,0,1,0,2,1,0,1,2,0,0,0,0,2,1,0,1,2,0,0,0,0,1,1,0,2,1,0, %T A278521 0,0,0,1,2,1,2,3,2,1,0,2,1,0,1,1,0,0,1,0,1,1,0,0,1,0,0,1,0,2,1,0,1,3, %U A278521 2,2,2,2,2,0,1,2,2,2,2,2,0,0,2,3,1,2,3,2,1,0,1,2,0,0,0,0,0,1,0,1,0,0,0,0,0,2,2,0,0,0,0,0,0,0,1,1,0,0,2,0,0 %N A278521 a(n) = A276573(n) - A278517(n). %H A278521 Antti Karttunen, <a href="/A278521/b278521.txt">Table of n, a(n) for n = 0..10028</a> %F A278521 a(n) = A276573(n) - A278517(n). %o A278521 (Scheme) (define (A278521 n) (- (A276573 n) (A278517 n))) %Y A278521 Cf. A276573, A278517, A278518, A278522. %K A278521 nonn %O A278521 0,2 %A A278521 _Antti Karttunen_, Nov 28 2016