A105467 Number of irregular primes less than or equal to the 3^n-th prime.

0, 0, 5, 22, 91, 286, 863, 2577, 7717, 23160, 69939, 209485, 627826, 1881554, 5645226, 16936048

Offset: 1

Author

Robert G. Wilson v, Apr 07 2005

Keywords

• hard
• nonn
• more

Comments

Limit_{n->inf.} a(n)/3^n = 1-e^(-1/2).

Crossrefs

Cf. A038833, A105458, A105462.

Programs

Mathematica

ip={ the list of irregular primes to 12 million }; Table[ Length[ Select[ip, # < Prime[3^n] &]], {n, 9}]

Extensions

Terms corrected and a(10)-a(16) added by Amiram Eldar, Mar 05 2019