

A055197


Numbers k such that A005728(k) is not prime.


4



10, 14, 16, 19, 20, 21, 25, 26, 27, 28, 30, 31, 32, 33, 34, 35, 38, 39, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 54, 56, 57, 58, 64, 65, 66, 67, 70, 71, 72, 73, 75, 76, 77, 78, 79, 80, 81, 82, 84, 85, 87, 88, 89, 90, 91, 92, 94, 95, 96, 98, 99, 100
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OFFSET

1,1


COMMENTS

From a question posed by Leo Moser.


REFERENCES

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


LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000
Leo Moser, Problem P42, Canadian Mathematical Bulletin, Vol. 5, No. 3 (1962), pp. 312313.


MATHEMATICA

s=1; Do[ s=s+EulerPhi[ n ]; If[ !PrimeQ[ s ], Print[ n ] ], {n, 1, 100} ]


CROSSREFS

Cf. A005728.
Complement of A055201.
Sequence in context: A067188 A092632 A213310 * A116610 A289698 A153041
Adjacent sequences: A055194 A055195 A055196 * A055198 A055199 A055200


KEYWORD

easy,nonn


AUTHOR

Robert G. Wilson v, Jul 04 2000


EXTENSIONS

Offset corrected by Amiram Eldar, Mar 01 2020


STATUS

approved



