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%I #13 Aug 30 2017 01:56:19
%S 87,260,130,65,194,97,290,145,434,217,650,325,974,487,1460,730,365,
%T 1094,547,1640,820,410,205,614,307,920,460,230,115,344,172,86,43,128,
%U 64,32,16,8,4,2,1,2,1,2,1,2,1,2,1
%N x -> x/2 if x even, x -> 3x - 1 if x odd.
%D R. K. Guy, Unsolved Problems in Number Theory, E16.
%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (0, 1).
%e 87 is odd, so it's followed by 3 * 87 - 1 = 260.
%e 260 is even, so it's followed by 260/2 = 130.
%t NestList[If[EvenQ[#], #/2, 3# - 1] &, 87, 100] (* _Alonso del Arte_, Aug 22 2017 *)
%Y Cf. A008879.
%K nonn,easy
%O 0,1
%A _N. J. A. Sloane_
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