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 A259728 #18 Sep 08 2022 08:46:13 %S A259728 0,3,6,9,15,18,27,30,33,36,39,45,48,51,54,57,60,63,66,69,81,84,87,90, %T A259728 93,96,99,105,108,126,129,135,138,150,153,156,159,165,168,177,180,183, %U A259728 186,189,195,198,225,228,252,261,264,267,270,273,282,291,294,297 %N A259728 Sum of digits of a(n) equals the sum of digits of 4*a(n). %C A259728 A007953(a(n)) = A007953(4*a(n)). %C A259728 a(n) is a multiple of 3, but not all multiples of 3 belong to the sequence: e.g., 12 = 4*3: A007953(12) = 1 + 2 = 3, but A007953(4*12) = A007953(48) = 4 + 8 = 12. %e A259728 15 belongs to the sequence, because A007953(15) = 6 = A007953(60) = A007953(4*15). %o A259728 (Magma) [n: n in [0..400] | &+Intseq(n) eq &+Intseq(4*n)]; // _Vincenzo Librandi_, Aug 05 2015 %Y A259728 Cf. A007953, A070279, A259727, A259729. %K A259728 nonn,base %O A259728 1,2 %A A259728 _Christina Steffan_, Jul 05 2015 %E A259728 More terms from _Vincenzo Librandi_, Aug 05 2015