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A089798
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Expansion of Jacobi theta function theta_4(q^2).
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2
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1, 0, -2, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, -2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, -2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, -2, 0, 0, 0
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OFFSET
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0,3
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LINKS
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FORMULA
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For n > 0, a(n) = 2*(floor(sqrt(n/2)) - floor(sqrt((n-1)/2)))*(-1)^floor(sqrt(n/2)). - Mikael Aaltonen, Jan 18 2015
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MATHEMATICA
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a[n_] := SeriesCoefficient[ EllipticTheta[4, 0, q^2], {q, 0, n}]; Table[a[n], {n, 0, 101}] (* Jean-François Alcover, Nov 12 2012 *)
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PROG
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(PARI) for(n=0, 50, print1(if(n==0, 1, 2*(floor(sqrt(n/2)) - floor(sqrt((n-1)/2)))*(-1)^floor(sqrt(n/2))), ", ")) \\ G. C. Greubel, Nov 20 2017
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CROSSREFS
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KEYWORD
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sign
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AUTHOR
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STATUS
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approved
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