A113505 Numbers not the sum of at most three perfect powers (A001597).

7, 15, 23, 87, 111, 119, 167, 335, 1391, 1455, 1607, 1679, 1991, 25887, 26375

Offset

1,1

Comments

Cannot be written in the form a^x + b^y + c^z with a, b, c >= 0 and x, y, z > 1.

a(16), if it exists, is larger than 10^8. - Giovanni Resta, May 07 2017

Links

Table of n, a(n) for n=1..15.

Eric Weisstein's World of Mathematics, Perfect Power

Eric Weisstein's World of Mathematics, Powerful Number.

Mathematica

lmt = 40000; s = Union@ Join[{0, 1}, Flatten@ Table[n^i, {n, 2, Sqrt@ lmt}, {i, 2, Log[n, lmt]}]]; t = Select[ Union[Plus @@@ Tuples[s, 3]], # < lmt + 1 &]; Complement[Range@ lmt, t] (* Robert G. Wilson v *)

Crossrefs

A056828 is a subset, A001694, A274459.

Sequence in context: A243582 A336819 A056828 * A184920 A076796 A056119

Adjacent sequences: A113502 A113503 A113504 * A113506 A113507 A113508

Keyword

nonn,more

Author

R. P. van der Hilst (R.P.vanderHilst(AT)students.uu.nl), Jan 12 2006

Extensions

Edited by Robert G. Wilson v, May 01 2006

Status

approved