A097000 - OEIS

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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

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Table of n, a(n) for n=1..30.

EXAMPLE

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.

MATHEMATICA

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

CROSSREFS

Cf. A000010, A000203, A062401, A096852.

Sequence in context: A361937 A009694 A275816 * A285894 A271481 A208849

Adjacent sequences: A096997 A096998 A096999 * A097001 A097002 A097003

KEYWORD

nonn

AUTHOR

Labos Elemer, Jul 21 2004

STATUS

approved