A281678 Numbers k that have no digits in common with k^7.

3, 7, 8, 33, 43, 77, 93, 272, 332, 662, 7757, 31333

Offset

1,1

Comments

All terms have last digit 2, 3, 7 or 8.

Sequence is likely to be finite. If it exists, a(13) > 10^7.

In this sequence, the only terms with no repeated digits are 3, 7, 8, 43, 93. - Altug Alkan, Jan 26 2017

Links

Table of n, a(n) for n=1..12.

Example

43 is a term because 43^7 = 271818611107 has no digit 4 or 3.

Maple

select(t -> convert(convert(t, base, 10), set) intersect convert(convert(t^7, base, 10), set) = {},
{seq(seq(10*i+j, j=[2, 3, 7, 8]), i=0..10^4});

Mathematica

Select[Range[40000], Intersection[IntegerDigits[#], IntegerDigits[ #^7]] == {}&] (* Vincenzo Librandi, Jan 27 2017 *)

Prog

(PARI) isok(n) = #setintersect(Set(digits(n)), Set(digits(n^7))) == 0; \\ Michel Marcus, Jan 26 2017

Crossrefs

Cf. A001015. Contains A253576.

Cf. A281148.

Sequence in context: A152057 A177689 A191611 * A118622 A101366 A217359

Adjacent sequences: A281675 A281676 A281677 * A281679 A281680 A281681

Keyword

nonn,more,base

Author

Robert Israel, Jan 26 2017

Status

approved