A105465 Number of irregular primes less than or equal to the 2^n-th prime.

0, 0, 0, 1, 6, 16, 47, 96, 206, 406, 823, 1626, 3244, 6454, 12798, 25715, 51779, 103315, 206649, 412883, 825395, 1650179, 3299610, 6600347, 13201348, 26403834

Offset

1,5

Comments

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

Links

Table of n, a(n) for n=1..26.

Mathematica

ip={ the list of irregular primes to 12 million }; Table[ Length[ Select[ip, # <= Prime[2^n] &]], {n, 19}]

Crossrefs

Cf. A000928, A033844, A105456, A105460.

Sequence in context: A126360 A264545 A296855 * A364676 A341657 A288572

Adjacent sequences: A105462 A105463 A105464 * A105466 A105467 A105468

Keyword

hard,nonn,more

Author

Robert G. Wilson v, Apr 07 2005

Extensions

Data corrected and a(20)-a(26) added by Amiram Eldar, Mar 05 2019

Status

approved