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 A075661 Let f(n) = lcd(n)-lpf(n), where lcd(n) is the largest common difference between consecutive divisors of n (ordered by size) and lpf(n) is the largest prime factor of n. Sequence gives number of iterations for f(n) to reach 0 or -1. 2
 1, 1, 1, 1, 1, 1, 1, 2, 2, 1, 1, 2, 1, 1, 2, 2, 1, 2, 1, 2, 2, 1, 1, 3, 3, 1, 3, 2, 1, 2, 1, 2, 2, 1, 3, 3, 1, 1, 2, 3, 1, 2, 1, 2, 4, 1, 1, 3, 4, 3, 2, 2, 1, 4, 3, 3, 2, 1, 1, 4, 1, 1, 4, 3, 3, 2, 1, 2, 2, 3, 1, 3, 1, 1, 5, 2, 4, 2, 1, 4, 3, 1, 1, 4, 3, 1, 2, 3, 1, 4, 4, 2, 2, 1, 3, 5, 1, 3, 4, 5 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,8 LINKS Michael De Vlieger, Table of n, a(n) for n = 1..10000 Jason Earls, Smarandache iterations of the first kind on functions involving divisors and prime factors, in Smarandache Notions Journal (2004), Vol. 14.1, pp 259-264. EXAMPLE a(24)=3 because 24 -> 9 -> 3 -> -1. MATHEMATICA Array[-1 + Length@ NestWhileList[Function[n, Max@ Differences@ # - SelectFirst[Reverse@ #, PrimeQ] &@ Divisors[n]], #, # > 0 &] &, 100] (* Michael De Vlieger, Mar 28 2018 *) CROSSREFS Cf. A074348. Sequence in context: A202205 A336123 A353849 * A206829 A319694 A335641 Adjacent sequences: A075658 A075659 A075660 * A075662 A075663 A075664 KEYWORD nonn AUTHOR Jason Earls, Sep 23 2002 STATUS approved

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Last modified September 22 21:28 EDT 2023. Contains 365531 sequences. (Running on oeis4.)