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 A245352 #14 Jul 31 2025 03:49:06 %S A245352 0,1,2,3,4,5,6,5,6,7,8,9,10,11,8,9,10,11,12,13,14,9,10,11,12,13,14,15, %T A245352 14,15,16,17,18,19,20,13,14,15,16,17,18,19,16,17,18,19,20,21,22,13,14, %U A245352 15,16,17,18,19,18,19,20,21,22,23,24,19,20,21,22,23,24 %N A245352 Sum of digits of n written in fractional base 7/5. %C A245352 The base 7/5 expansion is unique and thus the sum of digits function is well-defined. %H A245352 Amiram Eldar, <a href="/A245352/b245352.txt">Table of n, a(n) for n = 0..10000</a> %H A245352 <a href="/index/Ba#base_fractional">Index entries for sequences related to fractional bases</a>. %F A245352 a(n) = A007953(A024642(n)). %e A245352 In base 7/5 the number 14 is represented by 530 and so a(14) = 5 + 3 + 0 = 8. %t A245352 a[n_] := a[n] = If[n == 0, 0, a[5 * Floor[n/7]] + Mod[n, 7]]; Array[a, 100, 0] (* _Amiram Eldar_, Jul 31 2025 *) %o A245352 (Sage) # uses [basepqsum from A245355] %o A245352 [basepqsum(7,5,w) for w in [0..200]] %o A245352 (PARI) a(n) = if(n == 0, 0, a(n\7 * 5) + n % 7); \\ _Amiram Eldar_, Jul 31 2025 %Y A245352 Cf. A007953, A000120, A244040, A024642, A053828. %K A245352 nonn,base,easy %O A245352 0,3 %A A245352 _Hailey R. Olafson_, Jul 18 2014