A077091 When iteration of f[]=Phi[](Sigma[]-Phi[]) is started at composite initial values listed here it ends at a nonzero fixed point.

1, 4, 6, 8, 9, 10, 12, 14, 15, 16, 18, 20, 21, 22, 24, 25, 26, 27, 28, 30, 32, 33, 34, 35, 38, 39, 42, 44, 45, 46, 49, 51, 54, 55, 56, 57, 58, 62, 63, 65, 68, 69, 70, 74, 75, 77, 82, 85, 86, 87, 91, 93, 94, 95, 99, 104, 111, 115, 119, 121, 125, 129, 133, 134, 143, 145, 153

Offset

1,2

Links

Table of n, a(n) for n=1..67.

Example

n=30: FixedPointList={30,32,46,20,16,22,12,8,10,6,4},end=4; n=94:FixedPointList={94,42,24},end=24.

Mathematica

f[x_] := EulerPhi[DivisorSigma[1, x]-EulerPhi[x]] Do[s=NestList[f, n, 100]; s1=Part[s, 99]; s2=Part[s, 100]; If[Equal[s1, s2]&&!PrimeQ[n], Print[{n, s1}]], {n, 1, 1000}]

Crossrefs

Cf. A077090-A077100.

Sequence in context: A141468 A140347 A140209 * A340268 A340058 A174891

Adjacent sequences: A077088 A077089 A077090 * A077092 A077093 A077094

Keyword

nonn

Author

Labos Elemer, Oct 31 2002

Status

approved