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A055201 Numbers n such that A005728(n) is prime. 2
1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13, 15, 17, 18, 22, 23, 24, 29, 36, 37, 40, 53, 55, 59, 60, 61, 62, 63, 68, 69, 74, 83, 86, 93, 97, 107, 109, 115, 116, 117, 118, 123, 128, 129, 139, 142, 147, 153, 154, 157, 158, 162, 167, 170, 175, 179, 181, 182, 183, 193, 194, 196 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

From a question by Leo Moser.

REFERENCES

Martin Gardner, "The Last Recreations," Chapter entitled "Strong Laws of Small Primes," Copernicus, Springer-Verlag, NY 1997, page 199.

LINKS

Table of n, a(n) for n=1..63.

MATHEMATICA

s=1; Do[s = s + EulerPhi[n]; If[PrimeQ[s], Print[n]], {n, 200}]

CROSSREFS

Cf. A005728.

Sequence in context: A002244 A037173 A091897 * A213006 A072303 A242413

Adjacent sequences:  A055198 A055199 A055200 * A055202 A055203 A055204

KEYWORD

easy,nonn

AUTHOR

Robert G. Wilson v, Jul 04 2000

STATUS

approved

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Last modified February 17 00:49 EST 2020. Contains 331976 sequences. (Running on oeis4.)