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a(n) is smallest prime > 2*a(n-1), a(1) = 13.
2

%I #11 Jun 18 2018 03:26:09

%S 13,29,59,127,257,521,1049,2099,4201,8419,16843,33703,67409,134837,

%T 269683,539389,1078787,2157587,4315183,8630387,17260781,34521589,

%U 69043189,138086407,276172823,552345671,1104691373,2209382761

%N a(n) is smallest prime > 2*a(n-1), a(1) = 13.

%H Harry J. Smith, <a href="/A065546/b065546.txt">Table of n, a(n) for n = 1..200</a>

%t NextPrim[n_Integer] := Block[ {k = n + 1}, While[ !PrimeQ[k], k++ ]; Return[k]]; a[1] = 13; a[n_] := NextPrim[ 2*a[n - 1]]; Table[ a[n], {n, 1, 35} ]

%t NestList[NextPrime[2#]&,13,30] (* _Harvey P. Dale_, Feb 25 2015 *)

%o (PARI) { for (n=1, 200, if (n>1, a=nextprime(2*a), a=13); write("b065546.txt", n, " ", a) ) } \\ _Harry J. Smith_, Oct 21 2009

%K nonn

%O 1,1

%A _Robert G. Wilson v_, Nov 28 2001