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A070810 Numbers n such that phi(n-phi(n))=A054571(n) is a power of 2 and n is not a prime number. 2
4, 6, 8, 9, 10, 12, 14, 16, 18, 20, 22, 24, 25, 28, 32, 36, 38, 39, 40, 42, 44, 46, 48, 50, 55, 56, 58, 62, 64, 65, 72, 76, 77, 80, 84, 88, 92, 94, 96, 100, 112, 116, 118, 124, 128, 134, 144, 152, 158, 160, 165, 168, 176, 184, 188, 192, 200, 202, 224, 232, 235, 236 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..62.

EXAMPLE

n=168: 168-phi[168]=168-48-120,phi[120]=32, a power of 2.

MATHEMATICA

Do[s=EulerPhi[n-EulerPhi[n]]; If[IntegerQ[Log[2, s]]&&!PrimeQ[n], Print[n]], {n, 1, 256}]

CROSSREFS

Cf. A054571, A051953, A000010, A070556, A070806-A070812.

Sequence in context: A060679 A051234 A102554 * A227180 A129930 A128510

Adjacent sequences:  A070807 A070808 A070809 * A070811 A070812 A070813

KEYWORD

nonn

AUTHOR

Labos Elemer, May 08 2002

STATUS

approved

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Last modified April 19 16:18 EDT 2019. Contains 322282 sequences. (Running on oeis4.)