OFFSET
1,1
COMMENTS
Probably A111870 is this sequence with the exception of the term a(4) = 23. [Farideh Firoozbakht, May 07 2012]
For n from 5 to 28, a(n) = A111870(n-1). - Donovan Johnson, Oct 26 2012
The statement prime(k) > (prime(k+1)/prime(k))^k for k>=1 is a rewrite of the Firoozbakht conjecture (see link). [John W. Nicholson, Oct 27 2012]
Values of k are in A214935.
The logarithmic (base 10) graph seems to be linearly asymptotic to n with slope ~ 1/log(10) which would imply that: log(prime(k)) ~ n as n goes to infinity. [Copy of comment by N. J. A. Sloane, Aug 27 2010 for A111870, copied and corrected for prime(k) by John W. Nicholson, Oct 29 2012]
(prime(k+1)/prime(k))^k ~ e^merit(k), where merit(k) = (prime(k+1)-prime(k))/log(prime(k)). - Thomas Ordowski, Mar 18 2013
Subset of A002386. - John W. Nicholson, Nov 19 2013
Copied comment from A111870 (modified variable to k): (prime(k+1)/prime(k))^k > 1 + merit(k) for k > 2, where merit(k) = (prime(k+1)-prime(k))/log(prime(k)). [Thomas Ordowski, May 14 2012] : Copied and modified by John W. Nicholson, Nov 20 2013
LINKS
John W. Nicholson, Table of n, a(n) for n = 1..38
A. Kourbatov, Verification of the Firoozbakht conjecture for primes up to four quintillion, arXiv:1503.01744 [math.NT], 2015
Alexei Kourbatov, Upper Bounds for Prime Gaps Related to Firoozbakht’s Conjecture, arXiv preprint, 2015.
A. Kourbatov, Upper bounds for prime gaps related to Firoozbakht's conjecture, J. Int. Seq. 18 (2015) 15.11.2
Wikipedia, Firoozbakht’s conjecture
EXAMPLE
The sequence (prime(k+1)/prime(k))^k for k=1,2,... starts with:
*1.500, *2.777, 2.744, *6.098, 2.305, 5.001, 2.178, 4.611, *8.054, 1.948, ...,
where records are marked with *. The corresponding primes are a(1)=prime(1)=2, a(2)=prime(2)=3, a(3)=prime(4)=7, a(4)=prime(9)=23, ...
MATHEMATICA
t = {}; p = 2; best = 0; n = 0; While[n++; last = p; p = NextPrime[p]; p <= 100000, f = (p/last)^n; If[f > best, best = f; AppendTo[t, last]]]; t (* T. D. Noe, May 08 2012 *)
PROG
(PARI) record=0; for(n=1, 75, current=(A000101[n]/A002386[n]*1.)^A005669[n]; if(current>record, record=current; print1(A002386[n], ", "))) \\ Each sequence is read in as a vector as to overcome PARI's primelimit. John W. Nicholson, Dec 01 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
Thomas Ordowski, May 07 2012
EXTENSIONS
a(13)-a(25) from Donovan Johnson, May 08 2012
Definition corrected by Max Alekseyev, Oct 23 2012
Clarified definition with k as index of a(n)=prime(k) instead of index n, John W. Nicholson, Oct 24, 2012.
a(26)-a(28) from Donovan Johnson, Oct 26 2012
a(29)-a(38) from John W. Nicholson, Dec 01 2013
STATUS
approved