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A060610 Repeatedly apply Euler phi to the n-th prime; a(n) is the number of terms in the resulting iteration chain which are not powers of 2 (number of initial iterations until reaching the first power of 2). 0
0, 1, 1, 2, 2, 2, 1, 3, 3, 3, 2, 3, 2, 3, 4, 3, 4, 2, 3, 3, 3, 3, 3, 3, 2, 3, 2, 4, 4, 3, 4, 3, 2, 4, 4, 3, 3, 5, 4, 4, 4, 3, 4, 2, 4, 3, 3, 4, 4, 4, 4, 3, 2, 4, 1, 4, 4, 4, 4, 3, 5, 4, 3, 3, 3, 4, 3, 3, 5, 4, 3, 5, 3, 3, 5, 5, 3, 3, 3, 2, 4, 3, 4, 4, 4, 3, 3, 4, 4, 3, 5, 4, 6, 4, 4, 5, 5, 3, 4, 4, 4, 5, 4, 4, 4 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

LINKS

Table of n, a(n) for n=1..105.

FORMULA

a(n)=A049115[A000040(n)]

EXAMPLE

n=100,p(100)=541, Phi-iteration chain is {541,540,144,48,16,8,4,2,1} with 9 terms. The first 4 terms (541,540,144,48) are not powers of 2, som a(100)=4.

MATHEMATICA

Table[Count[FixedPointList[EulerPhi[#]&, Prime[n]], _?(!IntegerQ[ Log[ 2, #]]&)], {n, 110}] (* Harvey P. Dale, Sep 18 2016 *)

CROSSREFS

Cf. A000040, A000010, A049108, A049113, A049116, A049115, A003434.

Sequence in context: A209266 A269400 A130267 * A017125 A063276 A055253

Adjacent sequences:  A060607 A060608 A060609 * A060611 A060612 A060613

KEYWORD

easy,nonn

AUTHOR

Labos Elemer, Apr 13 2001

EXTENSIONS

Definition clarified by Harvey P. Dale, Sep 18 2016

STATUS

approved

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Last modified February 21 04:18 EST 2019. Contains 320371 sequences. (Running on oeis4.)