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Search: id:A125674
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| A125674 |
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For any number larger than 2, the primes reached when you start with n and concatenate the sum of its prime factors with its largest prime factor, then repeat the process until you eventually reach a prime, or print a -1 if you never do. |
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| 1, 2, 3, 127, 5, 53, 7, 3331, 137, 888691, 11, 73, 13, 97, -1, -1, 17, 83, 19, 489479, 107, 4523, 23, 12073, 157, 519509, 12073, 1913, 29, 157, 31, -1, 33643361, 448257236701, 127, 103, 37, 27023222702059, 1613, -1, 41, 127, 43, 1511, -1, -1, 47, 113, -1, 3631, 2017, 17401297, 53, 113, -1, 137, 511439, -1, 59
(list; graph; listen)
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OFFSET
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1,2
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REFERENCES
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J. Earls & J. Rogers, "I Sin Every Number", IF(Sid_Vicious == TRUE && Alan_Turing == TRUE){ERROR_Cyberpunk();}, Lulu Press, NY, 2007, p. 126.
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LINKS
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Amazon.com, IF(Sid_Vicious == TRUE && Alan_Turing == TRUE){ERROR_Cyberpunk();}(Title of book).
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EXAMPLE
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Start with 4. Its factors are 2 and 2. Sum them to get 4 and then concatenate that to its largest prime factor to get 42. It is not a prime. The factors of 42 are: 2, 3, 7. Sum them to get 12 and concatenate it with its largest prime factor to get 127. That number is prime. So a(4) = 127.
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CROSSREFS
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Cf. A037274.
Sequence in context: A065842 A065841 A051177 this_sequence A095841 A004865 A006286
Adjacent sequences: A125671 A125672 A125673 this_sequence A125675 A125676 A125677
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KEYWORD
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sign
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AUTHOR
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Jason Earls (zevi_35711(AT)yahoo.com), Jan 30 2007
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