A080828 - OEIS

%I #3 Oct 01 2013 17:57:36

%S 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,

%T 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,

%U 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

%N 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.

%C 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.

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

%o (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); ) ) }

%K easy,nonn,tabf

%O 2,2

%A _Cino Hilliard_, Mar 27 2003