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A049116 Repeatedly apply Euler phi to n; a(n) = highest power of 2 that is seen. 3
1, 2, 2, 4, 4, 2, 2, 8, 2, 4, 4, 4, 4, 2, 8, 16, 16, 2, 2, 8, 4, 4, 4, 8, 8, 4, 2, 4, 4, 8, 8, 32, 8, 16, 8, 4, 4, 2, 8, 16, 16, 4, 4, 8, 8, 4, 4, 16, 4, 8, 32, 8, 8, 2, 16, 8, 4, 4, 4, 16, 16, 8, 4, 64, 16, 8, 8, 32, 8, 8, 8, 8, 8, 4, 16, 4, 16, 8, 8, 32, 2, 16, 16, 8, 64, 4, 8, 16, 16, 8, 8, 8 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000

EXAMPLE

If n is a power of 2, then it is of largest exponent. If n=2400, then its phi-sequence is {2400,640,256,128,64,32,16,8,4,2,1}. The value of first power of 2 is 256. Thus a(2400)=256.

MATHEMATICA

Table[SelectFirst[NestWhileList[EulerPhi[#]&, n, #>1&], IntegerQ[Log[2, #]]&], {n, 120}] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Mar 23 2019 *)

CROSSREFS

Cf. A000010.

Sequence in context: A325445 A165207 A130501 * A065176 A060267 A214516

Adjacent sequences:  A049113 A049114 A049115 * A049117 A049118 A049119

KEYWORD

nonn

AUTHOR

Labos Elemer

STATUS

approved

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Last modified July 29 13:28 EDT 2021. Contains 346346 sequences. (Running on oeis4.)