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%I #67 Oct 25 2017 07:38:19
%S 2,5,11,23,47,97,197,397,797,1597,3203,6421,12853,25717,51437,102877,
%T 205759,411527,823117,1646237,3292489,6584983,13169977,26339969,
%U 52679969,105359939,210719881,421439783,842879579,1685759167,3371518343
%N a(1) = 2; a(n) is smallest prime > 2*a(n-1).
%C It appears that lim_{n->infinity} a(n)/2^n exists and is approximately 1.569985585.... - _Franklin T. Adams-Watters_, Nov 11 2011
%C This is a B_2 sequence. - _Thomas Ordowski_, Sep 23 2014 See the link.
%C Conjecture: lim_{n->infinity} a(n)/A006992(n) = 5.1648264... - _Thomas Ordowski_, Apr 05 2015
%H Zak Seidov and Michael De Vlieger, <a href="/A055496/b055496.txt">Table of n, a(n) for n = 1..1000</a> (First 100 terms from Zak Seidov)
%H V. Shevelev, <a href="http://www.cs.uwaterloo.ca/journals/JIS/VOL15/Shevelev/shevelev19.html">Ramanujan and Labos primes, their generalizations, and classifications of primes</a>, J. Integer Seq. 15 (2012), #12.5.4.
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/B2-Sequence.html">B_2-Sequence</a>.
%F a(n+1) = A060264(a(n)). - _Peter Munn_, Oct 23 2017
%p A055496 := proc(n) option remember; if n=1 then 2 else nextprime(2*A055496(n-1)); fi; end;
%t 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} ]
%t a[1]=2;a[n_]:=a[n]=Prime[PrimePi[2*a[n-1]]+1];Table[a[n],{n,40}] (* _Zak Seidov_, Feb 16 2006 *)
%t NestList[ NextPrime[2*# ]&,2,100] (* _Zak Seidov_, Jul 28 2009 *)
%o (PARI) print1(a=2);for(n=2,20,print1(", ",a=nextprime(a+a))) \\ _Charles R Greathouse IV_, Jul 19 2011
%Y Cf. A006992, A060264, A163963.
%Y Values of a(n)-2*a(n-1) in A163469. - _Zak Seidov_, Jul 28 2009
%Y Cf. A065545 (with a(1)=3). - _Zak Seidov_, Feb 04 2016
%Y Row 1 of A229608.
%K nonn
%O 1,1
%A _N. J. A. Sloane_, Jul 07 2000
%E Mathematica updated by _Jean-François Alcover_, Jun 19 2013
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