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 A050707 #30 Sep 08 2022 08:44:58
%S A050707 4,16,27,28,30,42,76,87,92,95,108,114,120,124,128,133,136,147,148,154,
%T A050707 172,196,202,204,216,222,238,242,243,244,245,255,256,260,285,286,292,
%U A050707 308,310,325,338,340,342,350,386,412,418,422,423,426,435,440,458,464
%N A050707 Composites c that reach a prime after 3 iterations of c -> c + sum of prime factors of c.
%H A050707 Vincenzo Librandi, <a href="/A050707/b050707.txt">Table of n, a(n) for n = 1..1001</a> [offset shifted by _Georg Fischer_, Oct 29 2019]
%e A050707 204 is a term:
%e A050707 Iteration 1: 204 = 2*2*3*17 so 204 + (2+2+3+17) = 204 + 24 = 228 and composite.
%e A050707 Iteration 2: 228 = 2*2*3*19 so 228 + (2+2+3+19) = 228 + 26 = 254 and composite.
%e A050707 Iteration 3: 254 = 2*127 so 254 + (2+127) = 254 + 129 = 383 and prime.
%t A050707 nxt[n_]:=Total[Flatten[Table[#[[1]],{#[[2]]}]&/@FactorInteger[n]]]+n; Select[ Range[500],PrimeQ[NestList[nxt,#,3]]=={False,False,False,True}&] (* _Harvey P. Dale_, Feb 23 2014 *)
%o A050707 (Magma) f:=func<n|n+(&+[j[1]*j[2]: j in Factorization(n)]) >; a:=[]; for k in [4..500] do if not IsPrime(k) and not IsPrime(f(k)) and not IsPrime(f(f(k))) and IsPrime(f(f(f(k)))) then Append(~a,k); end if; end for; a; // _Marius A. Burtea_, Oct 17 2019
%Y A050707 Cf. A050703, A050704, A050705, A050706, A050708, A050709, A050710.
%K A050707 nonn
%O A050707 1,1
%A A050707 _Patrick De Geest_, Aug 15 1999
%E A050707 Name edited by _Michel Marcus_, Oct 17 2019