A135693 Not the sum of three positive squares or cubes.

1, 2, 4, 5, 7, 8, 15, 23, 31, 87, 111, 119, 148, 167, 263, 311, 335, 391, 407, 455, 559, 599, 839, 951, 1159, 1231, 1287, 1303, 1391, 1455, 1463, 1607, 1660, 1679, 1751, 1863, 1991, 2351, 2615, 2799, 3247, 3983, 4327, 4367, 5199, 5655, 6047, 6159, 6351

Offset: 1

Author

Zak Seidov and Giovanni Resta, Feb 24 2008

Keywords

• nonn

Comments

No other terms < 10^9. Presumably the sequence is finite.

Sum can include a mix of squares and cubes. - James C. McMahon, Apr 19 2025

Links

• Chai Wah Wu, Table of n, a(n) for n = 1..82

Crossrefs

Cf. A113505, A135367.

Cf. A004214, A057904.

Programs

Mathematica

lim=40000; s=Range[Sqrt[lim]]^2; c=Range[Surd[lim, 3]]^3; A135693=Complement[Range[lim], Select[Total/@Tuples[Union[s, c], {3}], #<=lim&]] (* James C. McMahon, Apr 19 2025 *)

Extensions

Edited by N. J. A. Sloane, Mar 01 2008