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A160541 Number of odd-then-even runs to reach 1 under the modified `3x+1' map: n -> n/2 if n is even, n -> (3n+1)/2 if n is odd. 0

%I

%S 0,1,1,1,1,2,3,1,4,2,3,2,2,4,2,1,3,5,4,2,1,4,2,2,5,3,17,4,4,3,16,1,6,

%T 4,2,5,4,5,6,2,17,2,6,4,4,3,16,2,5,6,5,3,2,18,17,4,7,5,6,3,3,17,15,1,

%U 6,7,5,4,3,3,16,5,18,5,2,5,5,7,6,2,4,18,17,2,1,7,5,4,6,5,14,3,3,17,15,2,19

%N Number of odd-then-even runs to reach 1 under the modified `3x+1' map: n -> n/2 if n is even, n -> (3n+1)/2 if n is odd.

%C The 2->1 step is not counted.

%e 7->11->17->26->13->20->10->5->8->4->2->1, so the odd-then-even runs are (7->11->17->26) (13->20->10) (5->8->4->2), and a(7) is 3.

%t Table[Length[Split[Most[NestWhileList[T, i, #!=1&]], OddQ[ #1]||EvenQ[ #2]]], {i, 1, 100}]

%K nonn

%O 1,6

%A Brenton Bostick (bostick(AT)gmail.com), May 18 2009

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