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A070811 Numbers n such that phi(n-phi(n))=A054571(n) is not a power of 2 and n is not a prime number. 3
1, 15, 21, 26, 27, 30, 33, 34, 35, 45, 49, 51, 52, 54, 57, 60, 63, 66, 68, 69, 70, 74, 75, 78, 81, 82, 85, 86, 87, 90, 91, 93, 95, 98, 99, 102, 104, 105, 106, 108, 110, 111, 114, 115, 117, 119, 120, 121, 122, 123, 125, 126, 129, 130, 132, 133, 135, 136, 138, 140 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
EXAMPLE
n=30: phi[30]=8, cototient[30]=22,phi[22]=10 is not a power of 2.
MATHEMATICA
Do[s=EulerPhi[n-EulerPhi[n]]; If[ !IntegerQ[Log[2, s]]&&!PrimeQ[n], Print[n]], {n, 1, 256}]
CROSSREFS
Sequence in context: A020204 A280389 A057489 * A211375 A326387 A217078
KEYWORD
nonn
AUTHOR
Labos Elemer, May 08 2002
STATUS
approved

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Last modified July 18 21:02 EDT 2024. Contains 374388 sequences. (Running on oeis4.)