A097000 A062401(x)=phi[sigma(x)] function is iterated; initial value=2^n; a(n)=smallest term of trajectory.

2, 4, 8, 16, 32, 64, 128, 256, 432, 1024, 1728, 4096, 1800, 7200, 32768, 65536, 131072, 262144, 326592, 1036800, 1658880, 4194304, 4838400, 16777216, 33554432, 67108864, 82301184, 207360000, 361267200, 414720000

Offset: 1

Author

Labos Elemer, Jul 21 2004

Keywords

• nonn

Examples

			n=8: 2^n=256, list={256,432,480,432,...}, max=a(8)=256, the start value;
n=13:2^n=8192,list={8192,10584,8640,8064,6144,3456,[2560,1800,2880, 3024,3840,3456],2560,..}, min=1800=a(13), a term of 6-cycle.
		

Crossrefs

Cf. A000010, A000203, A062401, A096852.

Programs

Mathematica

fs[x_] :=EulerPhi[DivisorSigma[1, x]] itef[x_, hos_] :=NestList[fs, x, hos] Table[Min[itef[2^w, 200]], {w, 1, 30}]