A133420 Number of steps to reach 1 under repeated applications of the "5x+1" map of A133419, or -1 if 1 is never reached.

0, 1, 1, 2, 14, 2, 5, 3, 2, 15, 9, 3, 12, 6, 15, 4, 9, 3, 7, 16, 6, 10, 21, 4, 9, 13, 3, 7, 18, 16, 16, 5, 10, 10, 14, 4, 19, 8, 13, 17, 13, 7, 7, 11, 16, 22, 26, 5, 16, 10, 10, 14, 25, 4, 25, 8, 8, 19, 23, 17, 13, 17, 7, 6, 17, 11, 11, 11, 22, 15, 26, 5, 16, 20, 10, 9, 20, 14, 14, 18, 4, 14

Offset: 1

Author

N. J. A. Sloane, Nov 27 2007

Keywords

• nonn
• easy

Comments

The 5x+1 map sends x to x/2 if x is even, x/3 if x is divisible by 3, otherwise 5x+1.

Links

• R. J. Mathar, Table of n, a(n) for n = 1..20000
• R. J. Mathar, Maple program to make b-file
• Tomás Oliveira e Silva, The px+1 problem
• Index entries for sequences related to 3x+1 (or Collatz) problem

Crossrefs

Cf. A133419.