A064685 Length of orbit of 2n+1 in the 3x+1 problem.

1, 8, 6, 17, 20, 15, 10, 18, 13, 21, 8, 16, 24, 112, 19, 107, 27, 14, 22, 35, 110, 30, 17, 105, 25, 25, 12, 113, 33, 33, 20, 108, 28, 28, 15, 103, 116, 15, 23, 36, 23, 111, 10, 31, 31, 93, 18, 106, 119, 26, 26, 88, 39, 101, 114, 70, 13, 34, 21, 34, 96, 47, 109, 47, 122

Offset

0,2

Links

Table of n, a(n) for n=0..64.

Index entries for sequences related to 3x+1 (or Collatz) problem

Formula

f(n)= n/2 if n is even, 3n+1 if n is odd; stop if n is 1.

Example

E.g. orbit(3) = 3->10->5->16->8->4->2->1, so length of chain = 8

Prog

(ARIBAS): function a064685(maxarg: integer); var n: integer; begin for n := 1 to maxarg by 2 do write(length(orbit(n)), " "); end; end; a064685(140). For definition of function orbit see A064684.

Crossrefs

Sequence in context: A119876 A281718 A036176 * A300885 A300941 A075486

Adjacent sequences: A064682 A064683 A064684 * A064686 A064687 A064688

Keyword

nonn,easy

Author

Jon Perry, Oct 10 2001

Extensions

More terms from Klaus Brockhaus, Oct 13 2001

Status

approved