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%I #6 Mar 30 2012 18:34:55
%S 20,1,22,21,19,20,20,20,27,2,21,25,19,22,21,20,19,21,24,26,20,20,19,
%T 28,22,20,20,20,26,20,25,21,30,20,26,22,27,27,20,29,19,2,19,28,25,21,
%U 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
%N 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).
%t f[n_] := Flatten[ Table[ # [[1]], {1} ] & /@ FactorInteger[ 3n + 2 ]][[ -1]]; Table[ Length[ NestWhileList[f, n, UnsameQ, All]] - 1, {n, 1, 72}]
%Y Cf. A083557.
%K nonn
%O 1,1
%A _Robert G. Wilson v_ & _Jud McCranie_, Jun 11 2003
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