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URL: https://oeis.org/A194658

⇱ A194658 - OEIS

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A194658
a(n) is the maximal prime, such that for all primes x<=a(n) the number of primes in (x/2,x) is less than n.
11
2, 11, 17, 29, 41, 47, 59, 67, 71, 97, 101, 107, 109, 137, 151, 167, 179, 181, 191, 197, 233, 239, 241, 263, 269, 281, 283, 311, 347, 349, 367, 373, 401, 409, 419, 431, 433, 439, 461, 487, 491, 503, 521, 571, 587, 593, 599, 601, 607, 617, 643, 647, 653
OFFSET
1,1
COMMENTS
The next prime after a(n) is A080359(n+1).
LINKS
Vladimir Shevelev, Ramanujan and Labos primes, their generalizations and classifications of primes, arXiv:0909.0715 [math.NT], 2009-2011.
Jonathan Sondow, J. W. Nicholson, and T. D. Noe, Ramanujan Primes: Bounds, Runs, Twins, and Gaps, arXiv:1105.2249 [math.NT], 2011; J. Integer Seq. 14 (2011) Article 11.6.2.
FORMULA
A080359(n) <= a(n) <= A104272(n).
MATHEMATICA
b[1] = 2; b[n_] := b[n] = Module[{x = b[n-1]}, While[PrimePi[x] - PrimePi[ Quotient[x, 2]] != n, x++]; x];
a[n_] := NextPrime[b[n+1], -1];
Array[a, 100] (* Jean-François Alcover, Nov 11 2018 *)
CROSSREFS
Subsequence of A164368.
Sequence in context: A087379 A019364 A164368 * A104272 A214934 A233866
KEYWORD
nonn
AUTHOR
Vladimir Shevelev, Sep 01 2011
STATUS
approved