A074348 Smallest number requiring n steps to reach 0 or -1 when iterating the function: 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.

1, 8, 24, 45, 75, 160, 273, 429, 741, 1001, 1183, 1547, 2645, 3553, 4301, 5423, 10880, 23465, 33371, 39109, 49075, 74011, 98933, 104371, 107911, 163489, 263177, 371591, 409219, 420727, 631215, 986537, 1234459, 1440299, 2777775, 3101857, 3412783, 3626797

Offset

1,2

Links

Michael De Vlieger, Table of n, a(n) for n = 1..42

Jason Earls, Smarandache iterations of the first kind on functions involving divisors and prime factors, in Smarandache Notions Journal (2004), Vol. 14.1, page 261.

Mathematica

With[{s = Array[Length@ NestWhileList[Function[n, Max@ Differences@ # - SelectFirst[Reverse@ #, PrimeQ] &@ Divisors[n]], #, # > 0 &] &, 10^5]}, Array[FirstPosition[s, #][[1]] &, Max@ s - 1, 2]] (* Michael De Vlieger, Mar 28 2018 *)

Crossrefs

Cf. A075661.

Sequence in context: A173080 A051062 A152531 * A063403 A355433 A348119

Adjacent sequences: A074345 A074346 A074347 * A074349 A074350 A074351

Keyword

nonn

Author

Jason Earls, Sep 23 2002

Extensions

a(28)-a(38) from Michael De Vlieger, Mar 28 2018

Status

approved