A080828 Triangle read by rows in which n-th row gives trajectory of n (omitting n itself) under the map k -> 3k-1 if k odd, k -> k/2 if k even, stopping when reach 1, 5 or 17.

1, 8, 4, 2, 1, 2, 1, 14, 7, 20, 10, 5, 3, 8, 4, 2, 1, 20, 10, 5, 4, 2, 1, 26, 13, 38, 19, 56, 28, 14, 7, 20, 10, 5, 5, 32, 16, 8, 4, 2, 1, 6, 3, 8, 4, 2, 1, 38, 19, 56, 28, 14, 7, 20, 10, 5, 7, 20, 10, 5, 44, 22, 11, 32, 16, 8, 4, 2, 1, 8, 4, 2, 1, 50, 25, 74, 37, 110, 55, 164, 82, 41, 122

Offset

2,2

Comments

The 3x-1 problem terminates at 4,2,1 or 20,10,5 or 68,34,17. The x-1 problem terminates at 4,2,1 or 3,2,1.

Links

Table of n, a(n) for n=2..84.

Example

5->14->7->20->10->5 so 5th row is 14,7,20,10,5.

Prog

(PARI) x3nm1(n, p) = { print1(1" "); for(x=1, n, p1 = x; while(p1>1, if(p1%2==0, p1/=2, p1 = p1*p-1; ); print1(p1" "); if(p1 == 5 || p1 == 17, break); ) ) }

Crossrefs

Sequence in context: A197477 A381395 A133839 * A131916 A131606 A033328

Adjacent sequences: A080825 A080826 A080827 * A080829 A080830 A080831

Keyword

easy,nonn,tabf

Author

Cino Hilliard, Mar 27 2003

Status

approved