login
a(n) = A001221(A025586(n)), the number of distinct prime-factors of maximal term in 3x+1 iteration list started at n.
1

%I #11 Aug 28 2019 03:58:53

%S 0,1,1,1,1,1,2,1,2,1,2,1,2,2,2,1,2,2,2,2,1,2,2,2,2,2,2,2,2,2,2,1,2,2,

%T 2,2,2,2,2,2,2,1,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,1,2,2,2,2,

%U 2,2,2,2,2,2,3,2,2,2,2,2,2,2,2,3,1,2,2,2,2,2,2,2,3,2,2,2,2,2,2,2,2,2,2,2,2

%N a(n) = A001221(A025586(n)), the number of distinct prime-factors of maximal term in 3x+1 iteration list started at n.

%H G. C. Greubel, <a href="/A087976/b087976.txt">Table of n, a(n) for n = 1..1000</a>

%t Collatz[a0_Integer, maxits_: 1000] := NestWhileList[If[EvenQ[#], #/2, 3 # + 1] &, a0, Unequal[#, 1, -1, -10, -34] &, 1, maxits]; (*Collatz[n] function definition by Eric Weisstein*) A025586[m_] :=

%t Flatten[Table[Take[Sort[Collatz[n], Greater], 1], {n, m}]];

%t PrimeNu[A025586[100]] (* _G. C. Greubel_, Apr 24 2017 *)

%Y Cf. A001221, A025586, A087974, A087975.

%K nonn

%O 1,7

%A _Labos Elemer_, Sep 25 2003