A024640 n written in fractional base 7/3.

0, 1, 2, 3, 4, 5, 6, 30, 31, 32, 33, 34, 35, 36, 60, 61, 62, 63, 64, 65, 66, 320, 321, 322, 323, 324, 325, 326, 350, 351, 352, 353, 354, 355, 356, 610, 611, 612, 613, 614, 615, 616, 640, 641, 642, 643, 644, 645, 646, 3200, 3201, 3202, 3203, 3204, 3205, 3206, 3230, 3231

Offset: 0

Author

David W. Wilson

Keywords

• nonn
• base
• easy

Comments

To represent a number in base b, if a digit exceeds b-1, subtract b and carry 1. In fractional base a/b, subtract a and carry b.

Links

• Alois P. Heinz, Table of n, a(n) for n = 0..10000
• Index entries for sequences related to fractional bases.

Crossrefs

Cf. A245344.

Programs

Maple

a:= proc(n) `if`(n<1, 0, irem(n, 7, 'q')+a(3*q)*10) end:
seq(a(n), n=0..57);  # Alois P. Heinz, May 14 2021

Mathematica

a[n_] := a[n] = If[n == 0, 0, 10 * a[3 * Floor[n/7]] + Mod[n, 7]]; Array[a, 50, 0] (* Amiram Eldar, Aug 02 2025 *)

PARI

a(n) = if(n == 0, 0, 10 * a(n\7 * 3) + n % 7); \\ Amiram Eldar, Aug 02 2025