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 A252939 #7 Apr 18 2023 09:34:50 %S A252939 21,1,64,1,20,9,2,6,2,3,2,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,2,2,1,1,1, %T A252939 1,1,1,1,1,1,1,176,456,110,265,216,595,4,107,433,723,252,75,432,51, %U A252939 298,2405,780,431,866,78,135,723,29,842,224,5,467,672 %N A252939 First differences of A252912. %H A252939 Reinhard Zumkeller, <a href="/A252939/b252939.txt">Table of n, a(n) for n = 1..250</a> %o A252939 (Haskell) %o A252939 a252939 n = a252939_list !! (n-1) %o A252939 a252939_list = zipWith (-) (tail a252912_list) a252912_list %Y A252939 Cf. A252912, A252940 (run lengths). %K A252939 nonn %O A252939 1,1 %A A252939 _Reinhard Zumkeller_, Dec 25 2014