A176767 Smallest power of 7 whose decimal expansion contains n.

2401, 1, 2401, 343, 49, 823543, 16807, 7, 16807, 49, 96889010407, 117649, 13841287201, 13841287201, 11398895185373143, 4747561509943, 16807, 117649, 11398895185373143, 1977326743, 13841287201, 3909821048582988049

Offset

0,1

Comments

This is to 7 as A176763 is to 3 and as A030001 is to 2.

Links

Paolo Xausa, Table of n, a(n) for n = 0..10000

Formula

a(n) = MIN{A000420(i) such that n in decimal representation is a substring of A000420(i)}.

a(n) = 7^A062524(n). - Michel Marcus, Sep 30 2014

Example

a(1) = 1 because 7^0 = 1 has "1" as a substring (not a proper substring, though).
a(2) = 2401 because 7^4 = 2401 has "2" as a substring.
a(3) = 343 because 7^3 = 343 has "3" as a substring.

Mathematica

A176767[n_] := Block[{k = -1}, While[StringFreeQ[IntegerString[7^++k], IntegerString[n]]]; 7^k]; Array[A176767, 50, 0] (* Paolo Xausa, Apr 03 2024 *)

Crossrefs

Cf. A000420, A030001, A176763, A176764-A176773.

Sequence in context: A235259 A321638 A005073 * A018865 A186488 A186487

Adjacent sequences: A176764 A176765 A176766 * A176768 A176769 A176770

Keyword

base,easy,nonn

Author

Jonathan Vos Post, Apr 25 2010

Extensions

More terms from Sean A. Irvine and Jon E. Schoenfield, May 05 2010

Extended to a(0) by M. F. Hasler, Oct 03 2014

Status

approved