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 A230641 #18 Nov 28 2020 06:22:14
%S A230641 0,2,4,4,6,8,8,10,12,10,12,14,14,16,18,18,20,22,20,22,24,24,26,28,28,
%T A230641 30,32,28,30,32,32,34,36,36,38,40,38,40,42,42,44,46,46,48,50,48,50,52,
%U A230641 52,54,56,56,58,60,56,58,60,60,62,64,64,66,68,66,68,70,70,72,74,74,76,78,76,78,80,80,82,84,84,86,88,82
%N A230641 a(n) = n + (sum of digits in base-3 representation of n).
%C A230641 The image of this sequence is the set of nonnegative even numbers (A005843). Joshi (1973) proved that the sequence of base-q self numbers (analogous to A003052) is the sequence of odd numbers (A005408) for all odd q. - _Amiram Eldar_, Nov 28 2020
%D A230641 V. S. Joshi, Ph.D. dissertation, Gujarat Univ., Ahmedabad (India), October, 1973.
%D A230641 József Sándor and Borislav Crstici, Handbook of Number theory II, Kluwer Academic Publishers, 2004, Chapter 4, p. 384-386.
%H A230641 Donovan Johnson, <a href="/A230641/b230641.txt">Table of n, a(n) for n = 0..10000</a>
%H A230641 <a href="/index/Coi#Colombian">Index entries for Colombian or self numbers and related sequences</a>
%F A230641 a(n) = n + A053735(n). - _Amiram Eldar_, Nov 28 2020
%t A230641 Table[n + Plus @@ IntegerDigits[n, 3], {n, 0, 100}] (* _Amiram Eldar_, Nov 28 2020 *)
%o A230641 (Haskell)
%o A230641 a230641 n = a053735 n + n -- _Reinhard Zumkeller_, May 19 2015
%Y A230641 Related base-3 sequences: A053735, A134451, A230641, A230642, A230643, A230853, A230854, A230855, A230856, A230639, A230640, A010063 (trajectory of 1)
%Y A230641 Cf. A228088, A010061, A230091, A230092, A227915.
%K A230641 nonn,base
%O A230641 0,2
%A A230641 _N. J. A. Sloane_, Oct 31 2013