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 A048126 #12 Oct 17 2020 15:18:21
%S A048126 26,33,39,44,49,51,55,65,66,70,77,78,84,91,92,95,98,100,105,110,112,
%T A048126 114,119,120,125,126,128,129,130,132,135,140,143,144,150,154,156,160,
%U A048126 162,168,170,180,189,192,196,200,204,205,216,217,220,225,240,242,243
%N A048126 Becomes prime or 4 after exactly 4 iterations of f(x) = sum of prime factors of x.
%C A048126 f(x) = sum of prime factors with multiplicity, so that f(1500) = 2+2+3+5+5+5 = 22.
%H A048126 Harvey P. Dale, <a href="/A048126/b048126.txt">Table of n, a(n) for n = 1..1000</a>
%t A048126 spf[n_]:=Total[Flatten[Table[#[[1]],#[[2]]]&/@FactorInteger[n]]]; p4Q[n_] := Module[{lst=NestList[spf,n,4]},NoneTrue[Most[lst],PrimeQ] && NoneTrue[ Most[lst],#==4&]&&(PrimeQ[lst[[-1]]]||lst[[-1]]==4)]; Select[ Range[ 250],p4Q] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Oct 17 2020 *)
%K A048126 nonn
%O A048126 1,1
%A A048126 _David W. Wilson_