OFFSET

0,117

COMMENTS

This sequence is 13-regular.

More generally, if a/b is a rational number in the interval 5/3 <= a/b < 2 with gcd(b, 2) = 1 and gcd(a, b) = 1, then the lexicographically least sequence of nonnegative integers that avoids a/b-powers is (2 a - b)-regular.

LINKS

Eric Rowland, Table of n, a(n) for n = 0..20000

Lara Pudwell and Eric Rowland, Avoiding fractional powers over the natural numbers, arXiv:1510.02807 [math.CO] (2015).

FORMULA

a(13 n + 12) = a(n) + 1.

MATHEMATICA

(* This gives the first 2197 terms. *)

SubstitutionSystem[{n_ :> {0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, n + 1}}, {0}, {{3}}]

CROSSREFS

KEYWORD

nonn

AUTHOR

Eric Rowland, Oct 01 2016

STATUS

approved