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 A050779 #9 Oct 17 2019 22:41:32 %S A050779 2,3,5,7,13,37,43,61,67,73,97,101,137,139,157,163,173,181,193,197,199, %T A050779 211,223,233,257,277,281,283,307,347,349,353,367,379,389,397,409,421, %U A050779 433,457,463,487,499,547,557,563,577,601,613,617,641,643,661,673,677 %N A050779 Primes that are not ending primes after the iterated procedure of 'composite added to the sum of its prime factors reaches a prime'. %t A050779 a[n_]:=NestWhile[#+Total[Times@@@FactorInteger[#]]&,n,!PrimeQ[#]&]; t={}; Do[If[!PrimeQ[n],AppendTo[t,a[n]]],{n,4,nn=678}]; Complement[Prime[Range[PrimePi[nn]]],Select[Union[t],#<nn&]] (* _Jayanta Basu_, Jun 01 2013 *) %Y A050779 Cf. A050778, A050703-A050710. %K A050779 nonn %O A050779 1,1 %A A050779 _Patrick De Geest_, Sep 15 1999