cp's OEIS Frontend

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.

%I A080828 #3 Oct 01 2013 17:57:36
%S A080828 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 A080828 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 A080828 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 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.
%C A080828 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 A080828 5->14->7->20->10->5 so 5th row is 14,7,20,10,5.
%o A080828 (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 A080828 easy,nonn,tabf
%O A080828 2,2
%A A080828 _Cino Hilliard_, Mar 27 2003