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 A320519 #12 Oct 15 2018 05:09:37 %S A320519 2,1,-7,-26,449,3001,-81863,-790271,29441537,371653678,-17549650999, %T A320519 -273657699479,15647990550337,290477695697281,-19502273553366631, %U A320519 -419946226750915874,32375641678132277249,793304922112119056161,-69057016330377072921047,-1897210272812469982747199 %N A320519 a(n) = 2*n^n*cos(n*arcsin(sqrt(4*n^2-1)/(2*n))) for n > 0 and a(0) = 2. %F A320519 For n > 0, a(n) = n^n*(h(n)^(-n) + h(n)^n) where h(n) = (1 + i*sqrt(4*n^2 - 1))/(2*n). %F A320519 For n > 0, a(n) = 2 * n^n * cos(n*arctan(sqrt(4*n^2 - 1))). - _Vladimir Reshetnikov_, Oct 14 2018 %Y A320519 Cf. A320534. %K A320519 sign %O A320519 0,1 %A A320519 _Peter Luschny_, Oct 14 2018