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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
11, 17, 19, 23, 29, 31, 41, 47, 53, 59, 71, 79, 83, 89, 103, 107, 109, 113, 127, 131, 149, 151, 167, 179, 191, 227, 229, 239, 241, 251, 263, 269, 271, 293, 311, 313, 317, 331, 337, 359, 373, 383, 401, 419, 431, 439, 443, 449, 461, 467, 479, 491, 503, 509, 521 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
EXAMPLE
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.
MATHEMATICA
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 *)
CROSSREFS
Sequence in context: A050713 A217063 A038966 * A316100 A049593 A216664
KEYWORD
nonn
AUTHOR
Patrick De Geest, Sep 15 1999
STATUS
approved

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Last modified June 17 12:36 EDT 2024. Contains 373445 sequences. (Running on oeis4.)