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 A180416 Number of positive integers below 10^n, excluding perfect squares, which have a representation as a sum of 2 positive squares. 6
 3, 33, 298, 2649, 23711, 215341, 1982296, 18447847, 173197435, 1637524156, 15570196516, 148735628858, 1426303768587, 13722207893214, 132387231596281, 1280309591127436 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Numbers that can be represented as a sum of three or more positive squares but not as a sum of two positive squares (e.g., 3=1^2+1^2+1^2 or 6=1^2+1^2+2^2) are not counted. Numbers that can be represented as a sum of two positive squares and alternatively as a sum of three or more positive squares are counted (e.g., 18 = 9+9 = 1+1+16, 26, 41, ...). LINKS Eric W. Weisstein: MathWorld -- Lagrange's Four-Square Theorem. Eric W. Weisstein: MathWorld -- Sum of Squares Function. FORMULA a(n) = |{ 0

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Last modified October 18 23:39 EDT 2019. Contains 328211 sequences. (Running on oeis4.)