Search: id:A060715 Results 1-1 of 1 results found. %I A060715 %S A060715 0,1,1,2,1,2,2,2,3,4,3,4,3,3,4,5,4,4,4,4,5,6,5,6,6,6,7,7,6,7,7,7,7,8,8, %T A060715 9,9,9,9,10,9,10,9,9,10,10,9,9,10,10,11,12,11,12,13,13,14,14,13,13,12, %U A060715 12,12,13,13,14,13,13,14,15,14,14,13,13,14,15,15,15,15,15,15,16,15,16 %N A060715 Number of primes between n and 2n exclusive. %C A060715 See the additional references and links mentioned in A143227. [From Jonathan Sondow (jsondow(AT)alumni.princeton.edu), Aug 03 2008] %D A060715 M. Aigner and C. M. Ziegler, Proofs from The Book, Chapter 2, Springer NY 2001. %H A060715 T. D. Noe, Table of n, a(n) for n=1..1000 %H A060715 Math Olympiads, Bertrand's Postulate %H A060715 R. Chapman, Bertrand postulate %H A060715 S. Ramanujan, A Proof Of Bertrand's Postulate %H A060715 M. Slone, PlanetMath.org, Proof of Bertrand's conjecture %H A060715 Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics. %H A060715 Wolfram Research, Bertrand hypothesis %H A060715 Wikipedia, Proof of Bertrand's postulate %H A060715 C. K. Caldwell, The Prime Glossary, Bertrand's postulate %H A060715 Dr. Wilkinson, The Math Forum, Erdos' Proof %e A060715 a(35)=8 since eight consecutive primes (37,41,43,47,53,59,61,67) are located between 35 and 70. %p A060715 a := proc(n) local counter, i; counter := 0; from i from n+1 to 2*n-1 do if isprime(i) then counter := counter +1; fi; od; return counter; end: %o A060715 (PARI) { for (n=1, 1000, write("b060715.txt", n, " ", primepi(2*n - 1) - primepi(n)); ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Jul 10 2009] %Y A060715 Cf. A060756, A070046, A006992, A051501, A035250. %Y A060715 Cf. A101909 %Y A060715 Cf. A000720, A014085, A104272, A143223, A143224, A143225, A143226, A143227. [From Jonathan Sondow (jsondow(AT)alumni.princeton.edu), Aug 03 2008] %Y A060715 Sequence in context: A123505 A114920 A030361 this_sequence A108954 A123920 A029170 %Y A060715 Adjacent sequences: A060712 A060713 A060714 this_sequence A060716 A060717 A060718 %K A060715 nonn,easy %O A060715 1,4 %A A060715 Lekraj Beedassy (blekraj(AT)yahoo.com), Apr 25 2001 %E A060715 Corrected by Dug Eichelberger (dug(AT)mit.edu), Jun 04 2001. More terms from Larry Reeves (larryr(AT)acm.org), Jun 05 2001 Search completed in 0.002 seconds