A055201 Numbers k such that A005728(k) is prime.

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

Offset: 1

Author

Robert G. Wilson v, Jul 04 2000

Keywords

• easy
• nonn

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

• Amiram Eldar, Table of n, a(n) for n = 1..10000
• Leo Moser, Problem P42, Canadian Mathematical Bulletin, Vol. 5, No. 3 (1962), pp. 312-313.

Crossrefs

Cf. A005728.

Complement of A055197.

Programs

Mathematica

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