A057903 Positive integers that are not the sum of exactly two positive cubes.

1, 3, 4, 5, 6, 7, 8, 10, 11, 12, 13, 14, 15, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 29, 30, 31, 32, 33, 34, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 66, 67, 68, 69, 70, 71, 73, 74, 75, 76, 77, 78, 79

Offset: 1

Author

Eric W. Weisstein

Keywords

• nonn

Comments

Includes the cubes themselves (since a^3 = b^3 + c^3 has no solution, by the exponent 3 case of Fermat's Last Theorem), so is different from A022555.

Links

• Eric Weisstein's World of Mathematics, Cubic number.

Crossrefs

Cf. A022555, A000578.

Programs

Mathematica

pr[n_] := Select[ PowersRepresentations[n, 2, 3], FreeQ[#, 0]& ]; Select[ Range[80], pr[#] == {} &] (* Jean-François Alcover, Nov 08 2012 *)

Formula

Equals A022555 union A000578 - {0}.

Extensions

Edited by N. J. A. Sloane, Sep 28 2007