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 A050781 #21 Dec 25 2016 21:27:34
%S A050781 55,72,84,119,143,256,2106,2211,2279,3024,3150,3551,4284,6360,6500,
%T A050781 9350,10200,10285,10919,13560,14279,14351,15606,16463,17063,23595,
%U A050781 25011,27208,28208,28600,31460,33096,42180,44330,52320,53053,53824
%N A050781 Numbers k such that sopfr(k) = sopfr(k - sopfr(k)).
%C A050781 sopfr(k) = sum of the prime factors of k (with multiplicity).
%H A050781 Paolo P. Lava, <a href="/A050781/b050781.txt">Table of n, a(n) for n = 0..200</a>
%e A050781 sopfr(72) = 2+2+2+3+3 = 12 = 2+2+3+5 = sopfr(72 - sopfr(72)), so 72 is in the sequence.
%t A050781 sopf[n_]:=Module[{sopfn=Total[Times@@@FactorInteger[n]],m},m=n+sopfn;If[n==m-Total[Times@@@FactorInteger[m]],m,0]]; DeleteCases[Table[ sopf[n],{n,55000}],_?(#==0&)] (* _Harvey P. Dale_, Jun 15 2011 *)
%Y A050781 Cf. A001414, A050703-A050710, A050780.
%K A050781 nonn,nice
%O A050781 0,1
%A A050781 _Patrick De Geest_, Sep 15 1999
%E A050781 Edited by _Jon E. Schoenfield_, Dec 25 2016