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 A084923 Consider the sequence b(1) = n, b(k) is the greatest prime factor of 3*b(k-1)+2. It is conjectured that this always becomes cyclic; a(n) = length of cycle (or 0 if no cycle is reached). 1
 20, 1, 22, 21, 19, 20, 20, 20, 27, 2, 21, 25, 19, 22, 21, 20, 19, 21, 24, 26, 20, 20, 19, 28, 22, 20, 20, 20, 26, 20, 25, 21, 30, 20, 26, 22, 27, 27, 20, 29, 19, 2, 19, 28, 25, 21, 20, 21, 22, 25, 26, 20, 19, 20, 6, 20, 31, 22, 23, 20, 28, 21, 21, 23, 27, 20, 27, 22, 25, 20, 19, 22 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS MATHEMATICA f[n_] := Flatten[ Table[ # [[1]], {1} ] & /@ FactorInteger[ 3n + 2 ]][[ -1]]; Table[ Length[ NestWhileList[f, n, UnsameQ, All]] - 1, {n, 1, 72}] CROSSREFS Cf. A083557. Sequence in context: A003833 A040418 A140116 * A141589 A162153 A040419 Adjacent sequences:  A084920 A084921 A084922 * A084924 A084925 A084926 KEYWORD nonn AUTHOR Robert G. Wilson v & Jud McCranie, Jun 11 2003 STATUS approved

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Last modified September 25 13:01 EDT 2020. Contains 337344 sequences. (Running on oeis4.)