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 A349611 Number of solutions to x^2 + y^2 + z^2 + w^2 <= n^2, where x, y, z, w are positive odd integers. 2
 0, 0, 1, 1, 5, 11, 32, 44, 82, 120, 207, 277, 405, 541, 768, 966, 1272, 1592, 2087, 2489, 3103, 3719, 4588, 5348, 6386, 7522, 8891, 10175, 11909, 13623, 15818, 17742, 20278, 22720, 25923, 28917, 32361, 36031, 40368, 44488, 49400, 54358, 60377, 65835, 72341 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,5 LINKS FORMULA a(n) = [x^(n^2)] theta_2(x^4)^4 / (16 * (1 - x)). EXAMPLE a(4) = 5 since there are solutions (1,1,1,1), (3,1,1,1), (1,3,1,1), (1,1,3,1), (1,1,1,3). MATHEMATICA Table[SeriesCoefficient[EllipticTheta[2, 0, x^4]^4/(16 (1 - x)), {x, 0, n^2}], {n, 0, 44}] CROSSREFS Cf. A055403, A055410, A341423, A349609, A349610. Sequence in context: A236428 A106908 A107442 * A323867 A280540 A077917 Adjacent sequences:  A349608 A349609 A349610 * A349612 A349613 A349614 KEYWORD nonn AUTHOR Ilya Gutkovskiy, Nov 23 2021 STATUS approved

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Last modified August 18 10:21 EDT 2022. Contains 356211 sequences. (Running on oeis4.)