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A105467
Number of irregular primes less than or equal to the 3^n-th prime.
2
0, 0, 5, 22, 91, 286, 863, 2577, 7717, 23160, 69939, 209485, 627826, 1881554, 5645226, 16936048
OFFSET
1,3
COMMENTS
Limit_{n->inf.} a(n)/3^n = 1-e^(-1/2).
MATHEMATICA
ip={ the list of irregular primes to 12 million }; Table[ Length[ Select[ip, # < Prime[3^n] &]], {n, 9}]
CROSSREFS
KEYWORD
hard,nonn,more
AUTHOR
Robert G. Wilson v, Apr 07 2005
EXTENSIONS
Terms corrected and a(10)-a(16) added by Amiram Eldar, Mar 05 2019
STATUS
approved