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 A048130 #18 Nov 20 2023 15:59:00
%S A048130 1257,1556,1774,1982,2566,2649,4249,4405,4497,4645,5086,5169,5286,
%T A048130 5317,5462,5574,6070,6074,6382,6518,7064,7149,7197,7284,7694,7813,
%U A048130 7947,8043,8193,8593,8605,8852,8894,8902,8998,9057,9182,9562,9575,10232,10326
%N A048130 Becomes prime or 4 after exactly 8 iterations of f(x) = sum of prime factors of x.
%C A048130 f(x) = sum of prime factors with multiplicity, so that f(1500) = 2+2+3+5+5+5 = 22.
%C A048130 Getting 4 is rare (only 1 such instance in the first 5,000 terms). - _Harvey P. Dale_, Nov 19 2023
%H A048130 Harvey P. Dale, <a href="/A048130/b048130.txt">Table of n, a(n) for n = 1..5000</a>
%t A048130 fi[n_]:=Total[Flatten[Table[#[[1]],#[[2]]]&/@FactorInteger[n]]]; bpQ[n_]:=Boole[PrimeQ[NestList[ fi[#]&,n,8]]] =={0,0,0,0,0,0,0,0,1}||Nest[fi[#]&,n,7]==4; Select[Range[11000],bpQ] (* _Harvey P. Dale_, Nov 19 2023 *)
%K A048130 nonn
%O A048130 1,1
%A A048130 _David W. Wilson_