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 A261090 #5 Aug 10 2015 07:31:31 %S A261090 1,0,0,1,0,1,2,3,3,6,8,12,19,29,45,69,106,164,254,395,615,960,1500, %T A261090 2346,3672,5751,9012,14129,22159,34768,54578,85730,134763,212017, %U A261090 333860,526226,830230,1311088,2072264,3277910,5188460,8217094 %N A261090 First differences of A261091: a(n) = A261091(n+1) - A261091(n). %F A261090 a(n) = A261091(n+1) - A261091(n). %o A261090 (Scheme) (define (A261090 n) (- (A261091 (+ n 1)) (A261091 n))) %Y A261090 Cf. A261091. %K A261090 nonn %O A261090 0,7 %A A261090 _Antti Karttunen_, Aug 09 2015