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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
OFFSET
1,5
COMMENTS
Lim_{n->inf.} a(n)/2^n = 1 - e^(-1/2).
MATHEMATICA
ip={ the list of irregular primes to 12 million }; Table[ Length[ Select[ip, # <= Prime[2^n] &]], {n, 19}]
CROSSREFS
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