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 A230634 #12 May 25 2016 18:48:38 %S A230634 17,19,21,34,36,38,51,53,55,65,67,70,72,82,84,86,99,101,103,116,118, %T A230634 120,130,132,135,137,147,149,151,164,166,168,181,183,185,195,197,200, %U A230634 202,212,214,216,229,231,233,246,248,250,257,261,262,263,267,274,276,278,291,293,295,308,310,312,322,324,327,329,339 %N A230634 Numbers n such that m + (sum of digits in base-4 representation of m) = n has exactly two solutions. %H A230634 Donovan Johnson, <a href="/A230634/b230634.txt">Table of n, a(n) for n = 1..10000</a> %H A230634 <a href="/index/Coi#Colombian">Index entries for Colombian or self numbers and related sequences</a> %t A230634 etsQ[n_]:=Count[#+Total[IntegerDigits[#,4]]&/@Range[n-1],n]==2; Select[ Range[ 350],etsQ] (* _Harvey P. Dale_, May 25 2016 *) %Y A230634 Related base-4 sequences: A053737, A230631, A230632, A010064, A230633, A230634, A230635, A230636, A230637, A230638, A010065 (trajectory of 1) %K A230634 nonn,base %O A230634 1,1 %A A230634 _N. J. A. Sloane_, Oct 30 2013