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 A256489 #13 May 06 2015 17:46:42
%S A256489 8,8,3,13,3,7,11,11,3,7,11,4,12,8,3,16,3,7,11,4,12,8,3,8,13,8,3,13,3,
%T A256489 7,9,16,3,7,11,4,12,8,3,8,13,8,3,13,3,7,9,7,14,8,3,13,3,7,9,13,3,7,9,
%U A256489 6,10,7,5,20,3,7,11,4,12,8,3,8,13,8,3,13,3,7,9,7,14,8,3,13,3,7,9,13,3,7,9,6,10,7,5,10,15,8,3,13,3,7,9
%N A256489 First differences of A257509: a(n) = A257509(n+1) - A257509(n).
%C A256489 It seems that for all n >= 0, Sum_{k=1 .. 2^n} a(k) = 2^(n+3).
%H A256489 Antti Karttunen, <a href="/A256489/b256489.txt">Table of n, a(n) for n = 1..16384</a>
%F A256489 a(n) = A257509(n+1) - A257509(n).
%o A256489 (Scheme) (define (A256489 n) (- (A257509 (+ n 1)) (A257509 n)))
%o A256489 (Haskell)
%o A256489 a256489 n = a256489_list !! (n-1)
%o A256489 a256489_list = zipWith (-) (tail a257509_list) a257509_list
%o A256489 -- _Reinhard Zumkeller_, May 06 2015
%Y A256489 Cf. A257509, A256490.
%K A256489 nonn,hear
%O A256489 1,1
%A A256489 _Antti Karttunen_, May 03 2015