A024659 - OEIS

%I #11 Aug 05 2025 03:37:55

%S 0,1,2,3,4,5,6,7,8,9,40,41,42,43,44,45,46,47,48,49,80,81,82,83,84,85,

%T 86,87,88,89,420,421,422,423,424,425,426,427,428,429,460,461,462,463,

%U 464,465,466,467,468,469,800,801,802,803,804,805,806,807,808,809,840,841,842

%N n written in fractional base 10/4.

%C 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.

%H Amiram Eldar, <a href="/A024659/b024659.txt">Table of n, a(n) for n = 0..10000</a>

%H <a href="/index/Ba#base_fractional">Index entries for sequences related to fractional bases</a>.

%t a[n_] := a[n] = If[n == 0, 0, 10 * a[4 * Floor[n/10]] + Mod[n, 10]]; Array[a, 100, 0] (* _Amiram Eldar_, Aug 04 2025 *)

%o (PARI) a(n) = if(n == 0, 0, 10 * a(n\10 * 4) + n % 10); \\ _Amiram Eldar_, Aug 04 2025

%K nonn,base,easy

%O 0,3

%A _David W. Wilson_