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