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 A113505 Numbers not the sum of at most three perfect powers (A001597). 8
 7, 15, 23, 87, 111, 119, 167, 335, 1391, 1455, 1607, 1679, 1991, 25887, 26375 (list; graph; refs; listen; history; text; internal format)
 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 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: A177768 A243582 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

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Last modified February 18 02:15 EST 2019. Contains 320237 sequences. (Running on oeis4.)