A024650 - OEIS

%I #11 Aug 02 2025 06:26:06

%S 0,1,2,3,4,5,6,7,8,20,21,22,23,24,25,26,27,28,40,41,42,43,44,45,46,47,

%T 48,60,61,62,63,64,65,66,67,68,80,81,82,83,84,85,86,87,88,210,211,212,

%U 213,214,215,216,217,218,230,231,232,233,234,235,236,237,238,250,251,252,253

%N n written in fractional base 9/2.

%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="/A024650/b024650.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[2 * Floor[n/9]] + Mod[n, 9]]; Array[a, 50, 0] (* _Amiram Eldar_, Aug 02 2025 *)

%o (PARI) a(n) = if(n == 0, 0, 10 * a(n\9 * 2) + n % 9); \\ _Amiram Eldar_, Aug 02 2025

%Y Cf. A245345.

%K nonn,base,easy

%O 0,3

%A _David W. Wilson_