A081169 - OEIS

A081169

Triangle in which n-th row gives trajectory of n (including n itself) under the map x -> x/2 if x is even, x -> 3*x-1 if x is odd, stopping when reaching 1, 5 or 17.

1, 2, 1, 2, 1, 3, 8, 4, 2, 1, 4, 2, 1, 5, 14, 7, 20, 10, 5, 6, 3, 8, 4, 2, 1, 7, 20, 10, 5, 8, 4, 2, 1, 9, 26, 13, 38, 19, 56, 28, 14, 7, 20, 10, 5, 10, 5, 11, 32, 16, 8, 4, 2, 1, 12, 6, 3, 8, 4, 2, 1, 13, 38, 19, 56, 28, 14, 7, 20, 10, 5, 14, 7, 20, 10, 5, 15, 44, 22, 11, 32, 16, 8, 4, 2, 1, 16

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

COMMENTS

It is conjectured that the sequence will always end in one of three loops: 1, 2,1,1, ...; 5 14 7 20 10 5...; or 17 50 25 74 37 110 55 164 82 41 122 61 182 91 272 136 68 34 17...

LINKS

Table of n, a(n) for n=1..87.

PROG

(PARI) xnm3(n) = { print1(1" "2" "1" "); for(x=2, n, x1=x; print1(x1" "); while(x1>1, if(x1%2==0, x1/=2, x1 = 3*p-1); print1(x1" "); if(x1==5 || x1==17, break); ) ) }

CROSSREFS

Cf. A080825.

Sequence in context: A137752 A331917 A328318 * A225765 A300588 A345257

Adjacent sequences: A081166 A081167 A081168 * A081170 A081171 A081172

KEYWORD

easy,nonn,tabf

AUTHOR

Cino Hilliard, Apr 16 2003

STATUS

approved