OFFSET
1,4
COMMENTS
I.e. number of primes p such that (2^n + 2^(n-1)) < p < 2^(n+1).
Ratio a(n)/A036378(n) converges as follows: 1, 0.5, 0.5, 0.4, 0.428571, 0.538462, 0.478261, 0.488372, 0.493333, 0.489051, 0.490196, 0.489224, 0.494266, 0.488213, 0.492079, 0.492556, 0.492697, 0.493134, 0.493827, 0.493885, 0.494513, 0.494605, 0.494682, 0.495049, 0.495214, 0.495412, 0.495563, 0.495699, 0.49585, 0.495984, 0.496113, 0.496237, 0.496346
LINKS
MATHEMATICA
f[n_] := PrimePi[2^(n + 1)] - PrimePi[2^n + 2^(n - 1) - 1]; Array[f, 35] (* Robert G. Wilson v *)
PROG
(PARI) a(n)=primepi(2^(n+1))-primepi(2^n+2^(n-1)-1) \\ Charles R Greathouse IV, Sep 25 2012
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Jun 12 2004
EXTENSIONS
a(34) and a(35) from Robert G. Wilson v, Jan 24 2006
STATUS
approved