

A111943


Prime p with prime gap q  p of nth record CramerShanksGranville ratio, where q is smallest prime larger than p and CSG ratio is (qp)/(log p)^2.


6



13, 23, 113, 1327, 31397, 370261, 2010733, 20831323, 25056082087, 2614941710599, 19581334192423, 218209405436543, 1693182318746371
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OFFSET

1,1


COMMENTS

a(13) was discovered by Bertil Nyman in 1999.
Shanks conjectures that the ratio will never reach 1. Granville conjectures the opposite: that the ratio will exceed or come arbitrarily close to 2/e^gamma = 1.1229....


REFERENCES

R. K. Guy, Unsolved Problems in Theory of Numbers, SpringerVerlag, Third Edition, 2004, A8.


LINKS

Table of n, a(n) for n=1..13.
Andrew Granville, Harold CramÃ©r and the distribution of prime numbers, Scandanavian Actuarial J. 1 (1995), pp. 1228.
Thomas R. Nicely, First occurrence of a prime gap of 1000 or greater
Eric Weisstein's World of Mathematics, Prime Gaps.
Eric Weisstein's World of Mathematics, CramerGranville Conjecture.
Eric Weisstein's World of Mathematics, Shanks Conjecture (and Wolf Conjecture.)


EXAMPLE

n Ratio prime:
2 0.6103 23
3 0.6264 113
4 0.6575 1327
5 0.6715 31397
6 0.6812 370261
7 0.7025 2010733
8 0.7394 20831323
9 0.7953 25056082087
10 0.7975 2614941710599
11 0.8177 19581334192423
12 0.8311 218209405436543
13 0.9206 1693182318746371


PROG

(PARI) r=CSG=0; p=13; forprime(q=17, 1e8, if(qp>r, r=qp; t=r/log(p)^2; if(t>CSG, CSG=t; print1(p", "))); p=q) \\ Charles R Greathouse IV, Apr 07 2013


CROSSREFS

Subsequence of A002386.
Cf. A111870, A166363.
Sequence in context: A147443 A131447 A110196 * A039448 A089768 A185684
Adjacent sequences: A111940 A111941 A111942 * A111944 A111945 A111946


KEYWORD

nonn,hard


AUTHOR

N. J. A. Sloane, following emails from R. K. Guy and Ed Pegg, Jr., Nov 27 2005


EXTENSIONS

Corrected and edited (p_n could be misinterpreted as the nth prime) by Daniel Forgues, Nov 20 2009
Edited by Charles R Greathouse IV, May 14 2010


STATUS

approved



