| DATA
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1, -2, 2, -2, 1, -2, 2, -2, 3, 0, 2, -2, 2, -2, 0, -4, 2, -2, 2, 0, 1, -2, 4, -2, 0, -2, 2, -2, 3, -2, 2, 0, 2, -2, 0, -2, 4, -2, 2, 0, 2, -4, 0, -4, 0, -2, 2, -2, 1, 0, 4, -2, 2, 0, 2, -2, 2, -4, 2, 0, 3, -2, 2, -2, 0, 0, 2, -4, 2, 0, 2, -4, 2, -2, 0, 0, 2, -2, 4, -2, 4, -2, 0, -2, 0, -4, 0, -2, 1, 0, 2, -2, 4, -4, 0, -2, 2, 0, 4, 0, 2, -2, 2, -2, 1
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| MATHEMATICA
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a[ n_] := If[ n < 0, 0, With[ {m = 6 n + 1}, DivisorSum[ m, KroneckerSymbol[ -4, #] KroneckerSymbol[ 12, m/#] &]]]; (* Michael Somos, Nov 11 2015 *)
a[ n_] := SeriesCoefficient[ EllipticTheta[ 3, 0, x^3] QPochhammer[ x^2]^3 / QPochhammer[ -x]^2, {x, 0, n}]; (* Michael Somos, Nov 11 2015 *)
a[ n_] := SeriesCoefficient[ 2^(-1/2) x^(-1/8) EllipticTheta[ 2, Pi/4, x^(1/2)] EllipticTheta[ 3, 0, x^3] QPochhammer[ x, -x], {x, 0, n}]; (* Michael Somos, Nov 11 2015 *)
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