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 A077463 Number of primes p such that n < p < 2n-2. 3
 0, 0, 0, 1, 1, 1, 1, 2, 2, 3, 3, 3, 3, 3, 3, 4, 4, 4, 3, 4, 4, 5, 5, 5, 6, 6, 6, 7, 6, 6, 6, 7, 7, 7, 8, 8, 8, 9, 9, 9, 9, 9, 9, 9, 9, 10, 9, 9, 9, 10, 10, 11, 11, 11, 12, 13, 13, 14, 13, 13, 12, 12, 12, 12, 13, 13, 13, 13, 13, 14, 14, 14, 13, 13, 13, 14, 15, 15, 14, 15, 15, 15, 15, 15 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,8 COMMENTS a(n) > 0 for n > 3 by Bertrand's postulate (and Chebyshev's proof of 1852). - Jonathan Vos Post, Aug 08 2013 LINKS J. Sondow and E. Weisstein, Bertrand's Postulate, World of Mathematics M. Tchebichef, Memoire sur les nombres premiers, J. Math. Pures Appliq. 17 (1852) 366. EXAMPLE a(19) = 3, the first value smaller than a previous value, because the only primes between 19 and 2 * 19 - 2 = 36 are {23,29,31}. - Jonathan Vos Post, Aug 08 2013 MATHEMATICA a[n_] := PrimePi[2n - 2] - PrimePi[n]; a[1] = 0; Table[a[n], {n, 1, 100}] (* Jean-François Alcover, Oct 31 2012 *) CROSSREFS Cf. A060715. Sequence in context: A025792 A119447 A157720 * A084556 A084506 A071578 Adjacent sequences:  A077460 A077461 A077462 * A077464 A077465 A077466 KEYWORD nonn AUTHOR Eric W. Weisstein, Nov 05 2002 STATUS approved

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