A163665 Numbers n such that n=prime(phi(sigma(pi(n)))).

2, 3, 19, 37, 719, 1511, 5443, 69709, 386093, 1907819, 10777931, 17819101, 18653749, 56125547, 60163267, 98911811, 272887613, 567611663, 989060309, 2444540149

Offset

1,1

Comments

It is obvious that all terms are primes. There is no further term up to 5*10^9.

Links

Table of n, a(n) for n=1..20.

Mathematica

Do[If[n=Prime[m]; m==EulerPhi[DivisorSigma[1, PrimePi[n]]], Print[n]], {m, 235000000}]

Crossrefs

Cf. A000010, A000040, A000720, A000203, A163666.

Sequence in context: A178202 A135958 A265787 * A323786 A215381 A215377

Adjacent sequences: A163662 A163663 A163664 * A163666 A163667 A163668

Keyword

more,nonn

Author

Farideh Firoozbakht, Aug 04 2009

Status

approved