This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A024640 #12 Aug 02 2025 06:25:49 %S A024640 0,1,2,3,4,5,6,30,31,32,33,34,35,36,60,61,62,63,64,65,66,320,321,322, %T A024640 323,324,325,326,350,351,352,353,354,355,356,610,611,612,613,614,615, %U A024640 616,640,641,642,643,644,645,646,3200,3201,3202,3203,3204,3205,3206,3230,3231 %N A024640 n written in fractional base 7/3. %C A024640 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 A024640 Alois P. Heinz, <a href="/A024640/b024640.txt">Table of n, a(n) for n = 0..10000</a> %H A024640 <a href="/index/Ba#base_fractional">Index entries for sequences related to fractional bases</a>. %p A024640 a:= proc(n) `if`(n<1, 0, irem(n, 7, 'q')+a(3*q)*10) end: %p A024640 seq(a(n), n=0..57); # _Alois P. Heinz_, May 14 2021 %t A024640 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 *) %o A024640 (PARI) a(n) = if(n == 0, 0, 10 * a(n\7 * 3) + n % 7); \\ _Amiram Eldar_, Aug 02 2025 %Y A024640 Cf. A245344. %K A024640 nonn,base,easy %O A024640 0,3 %A A024640 _David W. Wilson_