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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
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*(2n-3)/(6*log(n)) -> infinity as n -> infinity. A corollary to this is that the number of primes is infinite.
Number of primes in row n of the triangle in A214084;
a(n) = Sum_{m=n^2..n^3} A010051(m). - Reinhard Zumkeller, Jul 07 2012
LINKS
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: A258602 A327065 A307605 * A080838 A244396 A182993
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