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 A245346 #18 Aug 04 2025 02:17:30 %S A245346 0,1,2,3,4,5,6,7,8,9,3,4,5,6,7,8,9,10,11,12,6,7,8,9,10,11,12,13,14,15, %T A245346 9,10,11,12,13,14,15,16,17,18,5,6,7,8,9,10,11,12,13,14,8,9,10,11,12, %U A245346 13,14,15,16,17,11,12,13,14,15,16,17,18,19,20,7,8,9 %N A245346 Sum of digits of n in fractional base 10/3. %C A245346 The base 10/3 expansion is unique, and thus the sum of digits function is well-defined. %H A245346 Amiram Eldar, <a href="/A245346/b245346.txt">Table of n, a(n) for n = 0..10000</a> %H A245346 <a href="/index/Ba#base_fractional">Index entries for sequences related to fractional bases</a>. %F A245346 a(n) = A007953(A024658(n)). - _Amiram Eldar_, Aug 04 2025 %e A245346 In base 10/3 the number 11 is represented by 31 and so a(11) = 3 + 1 = 4. %t A245346 a[n_] := a[n] = If[n == 0, 0, a[3 * Floor[n/10]] + Mod[n, 10]]; Array[a, 100, 0] (* _Amiram Eldar_, Aug 04 2025 *) %o A245346 (Sage) # uses [basepqsum from A245355] %o A245346 [basepqsum(10,3,y) for y in [0..200]] %o A245346 (PARI) a(n) = if(n == 0, 0, a(n\10 * 3) + n % 10); \\ _Amiram Eldar_, Aug 04 2025 %Y A245346 Cf. A007953, A024658. %K A245346 nonn,base,easy %O A245346 0,3 %A A245346 _James Van Alstine_, Jul 18 2014