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 A134739 Cubes of (positive numbers that are not the sum of three nonzero squares), that is, the terms of A004214, cubed. 4
 1, 8, 64, 125, 343, 512, 1000, 2197, 3375, 4096, 8000, 12167, 15625, 21952, 29791, 32768, 50653, 59319, 64000, 103823, 140608, 166375, 195112, 216000, 250047, 262144, 357911, 493039, 512000, 614125, 658503, 778688, 857375, 1000000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS This sequence was inspired by e-mail from Ray Chandler, Nov 07 2007. Original name was: Cubes which are not the sum of three nonzero squares. That definition would not include 125 = 5^2 + 6^2 + 8^2. - Robert Israel, Jan 12 2016 For "(cubes of positive numbers) that are not the sum of three nonzero squares", that is, the cubes in A004214, see A267189. - N. J. A. Sloane, Jan 18 2016 LINKS Robert Israel, Table of n, a(n) for n = 1..10000 FORMULA a(n) = A004214(n)^3. - Ray Chandler, Jan 29 2009 EXAMPLE 8 is in the sequence because it is not possible to express 2 as a sum of three nonzero squares and 2^3 = 8. 27 is not in the sequence because 3 = 1^2 + 1^2 + 1^2. MAPLE N:= 1000: # to get all terms <= N^3 A004214:= {\$1..N} minus {seq(seq(seq(a^2 + b^2 + c^2, c = b .. floor(sqrt(N-a^2-b^2))), b = a .. floor(sqrt(N-a^2))), a=1..floor(sqrt(N/2)))}: map(`^`, sort(convert(A004214, list)), 3); # Robert Israel, Jan 12 2016 MATHEMATICA searchMax = 16; Flatten[Position[Take[Rest[CoefficientList[Sum[x^(i^2), {i, searchMax}]^3, x]], searchMax^2], 0]]^3 (* Based on Ray Chandler's program for A004214, Alonso del Arte, Jan 12 2016 *) PROG (PARI) is(n) = { my(a, b) ; a=1; while(a^2+1

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Last modified October 15 19:25 EDT 2019. Contains 328037 sequences. (Running on oeis4.)