A098202 - OEIS

A098202

a(n) is the length of the iteration trajectory when the cototient function (A051953) is applied to the n-th primorial number (A002110(n)).

3, 5, 8, 12, 18, 20, 31, 32, 41, 43, 61, 65, 80, 77, 95, 125, 131, 125, 157, 173, 140, 192, 195, 221, 213, 212, 261, 269, 277, 300, 296, 321, 336, 329, 358, 367

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OFFSET

1,1

LINKS

Table of n, a(n) for n=1..36.

FORMULA

a(n) = A053475(A002110(n)). - Robert G. Wilson v, Sep 22 2004

EXAMPLE

n=3: list={30,22,12,8,4,2,1,0}, a(4)=8.

MATHEMATICA

g[x_] := x - EulerPhi[x]; f[x_] := Length[ FixedPointList[g, x]] - 1; q[x_] := Product[ Prime[j], {j, x}]; Table[ f[ q[n]], {n, 33}]

CROSSREFS

Cf. A051953, A053475, A002110.

Sequence in context: A265061 A265062 A265063 * A164653 A001973 A248374

Adjacent sequences: A098199 A098200 A098201 * A098203 A098204 A098205

KEYWORD

nonn

AUTHOR

Labos Elemer, Sep 22 2004

EXTENSIONS

More terms from Robert G. Wilson v, Sep 22 2004

STATUS

approved