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%I #8 Jun 11 2017 20:23:13
%S 4,-16,56,-160,404,-944,2072,-4320,8648,-16720,31360,-57312,102364,
%T -179104,307672,-519808,864960,-1419456,2299832,-3682400,5831784,
%U -9141808,14194200,-21842368,33329700,-50456352,75813240,-113107872,167616832,-246811504,361218392,-525598496
%N Expansion of k/q^(1/2) in powers of q, where k is the elliptic function defined by sqrt(k) = theta_2/theta_3.
%C The elliptic modulus k is often used in elliptic integrals. - _Michael Somos_, Jun 11 2017
%F a(n) = 4*A001938(n).
%F k = q^(1/2) - 16*q^(3/2) + 56*q^(5/2) - 160*q^(7/2) + ... where the nome q = e^(-Pi*K'/K). - _Michael Somos_, Jun 11 2017
%Y See A001938, the main entry for this sequence, for further information.
%K sign
%O 0,1
%A _N. J. A. Sloane_, Apr 01 2007