A075486 Length of iteration list when Collatz-function is iterated with initial value 2^n + 1.

8, 6, 20, 13, 27, 28, 122, 123, 36, 37, 157, 114, 53, 54, 99, 100, 101, 102, 103, 73, 167, 168, 169, 170, 171, 172, 248, 174, 188, 189, 252, 253, 179, 180, 318, 244, 196, 197, 154, 155, 156, 157, 401, 327, 496, 497, 162, 163, 332, 333, 409, 472, 411, 412, 338

Offset: 1

Author

Labos Elemer, Sep 26 2002

Keywords

• nonn

Comments

n=4, 1+2^n = 17, list = {17, 52, 26, 13, 40, 20, 10, 5, 16, 8, 4, 2, 1}, so a(4) = 13.

Links

• T. D. Noe, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A006370, A008908, A074472, A075487-A075488.

Programs

Mathematica

Collatz[n_] := NestWhileList[If[EvenQ[#], #/2, 3 # + 1] &, n, # > 1 &]; Table[Length[Collatz[2^n + 1]], {n, 100}] (* T. D. Noe, Jan 17 2013 *)

Formula

a(n) = A008908(2^n+1).