OFFSET
1,1
COMMENTS
It appears that lim_{n->infinity} a(n)/2^n exists and is approximately 1.569985585.... - Franklin T. Adams-Watters, Nov 11 2011
This is a B_2 sequence. - Thomas Ordowski, Sep 23 2014 See the link.
Conjecture: lim_{n->infinity} a(n)/A006992(n) = 5.1648264... - Thomas Ordowski, Apr 05 2015
LINKS
Zak Seidov and Michael De Vlieger, Table of n, a(n) for n = 1..1000 (First 100 terms from Zak Seidov)
V. Shevelev, Ramanujan and Labos primes, their generalizations, and classifications of primes, J. Integer Seq. 15 (2012), #12.5.4.
Eric Weisstein's World of Mathematics, B_2-Sequence.
FORMULA
a(n+1) = A060264(a(n)). - Peter Munn, Oct 23 2017
MATHEMATICA
NextPrim[n_Integer] := Block[ {k = n + 1}, While[ !PrimeQ[k], k++ ]; Return[k]]; a[1] = 2; a[n_] := NextPrim[ 2*a[n - 1]]; Table[ a[n], {n, 1, 31} ]
a[1]=2; a[n_]:=a[n]=Prime[PrimePi[2*a[n-1]]+1]; Table[a[n], {n, 40}] (* Zak Seidov, Feb 16 2006 *)
NestList[ NextPrime[2*# ]&, 2, 100] (* Zak Seidov, Jul 28 2009 *)
PROG
(PARI) print1(a=2); for(n=2, 20, print1(", ", a=nextprime(a+a))) \\ Charles R Greathouse IV, Jul 19 2011
CROSSREFS
Values of a(n)-2*a(n-1) in A163469. - Zak Seidov, Jul 28 2009
Cf. A065545 (with a(1)=3). - Zak Seidov, Feb 04 2016
Row 1 of A229608.
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Jul 07 2000
EXTENSIONS
Mathematica updated by Jean-François Alcover, Jun 19 2013
STATUS
approved