login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A105465 Number of irregular primes less than or equal to the 2^n-th prime. 2
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 (list; graph; refs; listen; history; text; internal format)
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 * A288572 A301978 A275585

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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified April 8 19:37 EDT 2020. Contains 333323 sequences. (Running on oeis4.)