

A079648


Number of primes between n^2 and n^3.


2



0, 0, 2, 5, 12, 21, 36, 53, 79, 107, 143, 187, 235, 288, 356, 428, 510, 595, 699, 810, 929, 1062, 1206, 1358, 1528, 1707, 1898, 2098, 2323, 2561, 2807, 3066, 3340, 3636, 3946, 4283, 4611, 4975, 5351, 5755, 6162, 6587, 7034, 7506, 7998, 8504, 9042, 9587, 10157
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OFFSET

0,3


COMMENTS

There is always a prime between n^2 and n^3 for n > 1. For n = 2, primes 5 and 7 are between 4 and 8. For n > 2, we have the number of primes between n^2 and n^3 ~ n^3/log(n^3)  n^2/log(n^2) = n^2(2n3)/(6log(n)) > infinity as n > infinity. A corollary to this is the number of primes are infinite.
Number of primes in row n of the triangle in A214084;
a(n) = sum (A010051(m): n^2 <= m <= n^3).  Reinhard Zumkeller, Jul 07 2012


LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 0..110


EXAMPLE

For n = 4 4^2 = 16, 4^3 = 64. there are 12 primes between 16 and 64 namely, 17,19,23,29,31,37,41,43,47,53,59,61


PROG

(PARI) /* Count primes between x^2 and x^3. */ primex2x3(m, n) = { local(x, y, c); for(x=m, n, c=0; for(y=x^2, x^3, if(ispseudoprime(y), c++) ); print(c) ) }
(Haskell)
a079648 = sum . map a010051 . a214084_row  Reinhard Zumkeller, Jul 07 2012


CROSSREFS

Sequence in context: A276478 A095306 A258602 * A080838 A244396 A182993
Adjacent sequences: A079645 A079646 A079647 * A079649 A079650 A079651


KEYWORD

nonn


AUTHOR

Cino Hilliard, Jan 22 2003, Aug 23 2007


EXTENSIONS

Edited by N. J. A. Sloane, Aug 22 2009 at the suggestion of Richard Stanley


STATUS

approved



