A137850 a(n) = n base 5, under morphism f(1) = 121, f(2) = 123, f(3) = 141, f(4) = 142, or 0 if n base 5 has a zero.

121, 123, 141, 142, 0, 121121, 121123, 121141, 121142, 0, 123121, 123123, 123141, 123142, 0, 141121, 141123, 141141, 141142, 0, 142121, 142123, 142141, 142142, 0, 0, 0, 0, 0, 0, 121121121, 121121123, 121121141, 121121142, 0, 121123121, 121123123, 121123141

Offset

1,1

Links

Table of n, a(n) for n=1..38.

James Currie, Narad Rampersad, Dejean's conjecture holds for n >= 30, arXiv:0806.0044 [math.NT], May 30 2008.

Formula

a(n) = A007091(n) under the morphism f(1) = 121, f(2) = 123, f(3) = 141, f(4) = 142, or 0 if n base 5 is not a word in the alphabet {1,2,3,4}* i.e., has a zero.

Mathematica

a[n_] := Block[{d = IntegerDigits[n, 5]}, If[Min[d] == 0, 0, FromDigits[ Flatten[d /. {1 -> {1, 2, 1}, 2 -> {1, 2, 3}, 3 -> {1, 4, 1}, 4 -> {1, 4, 2}}]]]]; Array[a, 38] (* Giovanni Resta, Jun 20 2016 *)

Crossrefs

Cf. A007091.

Sequence in context: A137517 A364804 A014735 * A262517 A036231 A055468

Adjacent sequences: A137847 A137848 A137849 * A137851 A137852 A137853

Keyword

base,easy,nonn

Author

Jonathan Vos Post, Jun 03 2008

Extensions

Data corrected by Giovanni Resta, Jun 20 2016

Status

approved