E₄ eq H sum sq
E₄_eq_H_sum_sq
Plain-language statement
E₄.toFun = H₂² + H₂H₄ + H₄². Both are weight-4 level-1 modular forms tending to 1 at ∞, so their difference is a weight-4 cusp form, hence zero.
Source project: Sphere Packing in Dimension 8
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