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Primes in the chain of repeated application of x->2*x+3, starting at x=2.
5

%I #16 Sep 08 2022 08:45:50

%S 7,17,37,157,317,1277,2557,20477,655357,5242877,671088637,2684354557,

%T 5368709117,343597383677,23058430092136939517,23611832414348226068477,

%U 48357032784585166988247037,830767497365572420564879412675215357

%N Primes in the chain of repeated application of x->2*x+3, starting at x=2.

%H Vincenzo Librandi, <a href="/A172156/b172156.txt">Table of n, a(n) for n = 1..37</a>

%t Rest[Select[NestList[2#+3&,2,500],PrimeQ]] (* _Harvey P. Dale_, Nov 17 2012 *)

%o (Magma) x:=2; a:=[n eq 1 select 2*x+3 else 2*Self(n-1)+3: n in [1..120]]; [a[i]: i in [1..#a] | IsPrime(a[i])]; // _Bruno Berselli_, May 14 2013

%Y Cf. A154117. [_Klaus Brockhaus_, Feb 28 2010]

%K nonn

%O 1,1

%A _Vincenzo Librandi_, Jan 27 2010