%I #10 Oct 20 2019 22:44:16
%S 4,8,4,16,20,24,4,32,4,40,4,48,52,56,20,64,68,72,4,80,84,88,4,96,100,
%T 104,4,112,116,40,4,128,132,136,20,144,148,152,4,160,4,168,4,176,180,
%U 184,4,192,196,200,4,208,212,8,4,224,228,232,4,240,244,8,4,256,260,264
%N a(n) = gcd(4n, A025586(4n)), greatest common divisor of 4n and largest value in 3x+1 iteration list started at 4n.
%t c[x_] := (1-Mod[x, 2])*(x/2)+Mod[x, 2]*(3*x+1)c[1]=1; fpl[x_] := Delete[FixedPointList[c, x], -1] Table[GCD[4*w, Max[fpl[4*w]]], {w, 1, 256}]
%Y Cf. A025586, A033496-A087261.
%K nonn
%O 1,1
%A _Labos Elemer_, Sep 09 2003
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