A097002 A062402(x)=sigma(phi[x]) function is iterated; initial value=2^n; a(n)=smallest term of trajectory.

1, 3, 7, 15, 31, 63, 127, 255, 511, 1023, 2047, 4095, 8191, 6045, 24552, 65535, 131071, 262143, 524287, 1048575, 2097151, 4194303, 8388607, 16777215, 33554431, 67108863, 134217727, 268435455, 536870911, 1073741823

Offset

1,2

Links

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

Example

n=13: 2^n=8192, trajectory ={8192, 8191, 26208, [20440], 20440, .. a[13]=8191 arose in transient.

Mathematica

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

Crossrefs

Cf. A000010, A000203, A062402, A096857.

Sequence in context: A043764 A213248 A336700 * A060152 A126646 A225883

Adjacent sequences: A096999 A097000 A097001 * A097003 A097004 A097005

Keyword

nonn

Author

Labos Elemer, Jul 21 2004

Status

approved