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 A136577 #3 Mar 30 2012 18:59:20 %S A136577 1,1,0,-16,-256,-4096,0,16777216,4294967296,1099511627776,0, %T A136577 -1152921504606846976,-4722366482869645213696, %U A136577 -19342813113834066795298816,0,5192296858534827628530496329220096,340282366920938463463374607431768211456 %N A136577 Conjectured Hankel transform of A136576(n+1). %C A136577 a(n+1) is the Hankel transform of A086616. [From _Paul Barry_, Jun 03 2009] %F A136577 a(n)=4^floor(n^2/2)*((1/2-sqrt(2)/2)*cos(3*pi*n/4)+(1/2+sqrt(2)/2)*cos(pi*n/4)); %K A136577 easy,sign %O A136577 0,4 %A A136577 _Paul Barry_, Jan 08 2008