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 A050778 Primes that are ending primes after the iterated procedure of 'composite added to the sum of its prime factors reaches a prime'. 2

%I #12 Oct 17 2019 22:54:26

%S 11,17,19,23,29,31,41,47,53,59,71,79,83,89,103,107,109,113,127,131,

%T 149,151,167,179,191,227,229,239,241,251,263,269,271,293,311,313,317,

%U 331,337,359,373,383,401,419,431,439,443,449,461,467,479,491,503,509,521

%N Primes that are ending primes after the iterated procedure of 'composite added to the sum of its prime factors reaches a prime'.

%e 383 is ending prime for the following composites 182, 204, 218, 226, 228, 254, 329 and 341. For instance 341 (=11*31) -> 341 + (11+31) = 341 + 42 = 383.

%t a[n_]:=NestWhile[#+Total[Times@@@FactorInteger[#]]&,n,!PrimeQ[#]&]; t={}; Do[If[!PrimeQ[n],AppendTo[t,a[n]]],{n,4,nn=522}]; Select[Union[t],#<nn&] (* _Jayanta Basu_, Jun 01 2013 *)

%Y Cf. A050779, A050703-A050710.

%K nonn

%O 1,1

%A _Patrick De Geest_, Sep 15 1999

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Last modified July 12 09:57 EDT 2024. Contains 374239 sequences. (Running on oeis4.)