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 A057446 To get next term, multiply by 13, add 1 and discard any prime factors < 13. 14
 73, 19, 31, 101, 73, 19, 31, 101, 73, 19, 31, 101, 73, 19, 31, 101, 73, 19, 31, 101, 73, 19, 31, 101, 73, 19, 31, 101, 73, 19, 31, 101, 73, 19, 31, 101, 73, 19, 31, 101, 73, 19, 31, 101, 73, 19, 31, 101, 73, 19, 31, 101, 73, 19, 31, 101, 73, 19, 31, 101 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS This is the '13x+1' map. The 'Px+1 map': if x is divisible by any prime < P then divide out these primes one at a time starting with the smallest; otherwise multiply x by P and add 1. REFERENCES Murad A. AlDamen, Smarandache Notion Journal, "Murad iterating function" [details?]. Murad A. AlDamen, Murad iterating function, Journal of University of Jerash, 2001, to appear. LINKS Eric Weisstein's World of Mathematics, Collatz problem EXAMPLE 73 -> 13*73+1 = 950 = 2*5^2*19 -> 19, so second term is 19. MATHEMATICA m13[n_]:=First[Times@@@Select[FactorInteger[13 n+1], #[[1]]>11&]]; NestList[ m13, 73, 80] (* or *) PadRight[{}, 80, {73, 19, 31, 101}] (* Harvey P. Dale, Apr 16 2019 *) CROSSREFS Cf. A057216, A057522 (long version), A057534, A057614. Sequence in context: A051325 A249276 A102050 * A033393 A153646 A179516 Adjacent sequences:  A057443 A057444 A057445 * A057447 A057448 A057449 KEYWORD nonn AUTHOR Murad A. AlDamen (Divisibility(AT)yahoo.com), Oct 17 2000 STATUS approved

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Last modified October 20 10:23 EDT 2019. Contains 328257 sequences. (Running on oeis4.)