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%I #22 Sep 01 2022 16:38:01
%S 3,3,5,7,3,3,5,3,23,13,29,3,5,7,5,37,53,3,11,7,11,37,71,73,5,7,17,13,
%T 23,3,239,43,113,163,59,3,89,349,5,97,3,73,11,67,101,19,101,61,23,7,
%U 17,7,233,127,5,541,29,103,71,31,53,109,179,163,71,3,929,31,23,193,101,127
%N Least odd prime p such that 1 + p*2^n is also prime.
%C Let q = 1 + a(n)*2^n. Then q is least prime such that A098006(pi(q)) = 2^(n-1). See A134854 for the values of q.
%C a(n) = prime(k) for some k < 5*n for n <= 10000 . - _Pierre CAMI_, Jul 20 2014
%H Pierre CAMI, <a href="/A134855/b134855.txt">Table of n, a(n) for n = 1..10000</a> (First 1000 terms from T. D. Noe)
%t Table[Select[Prime[Range[2,10000]], PrimeQ[1+2^k # ]&, 1][[1]], {k,100}]
%t lop[n_]:=Module[{k=3,c=2^n},While[!PrimeQ[1+k*c],k=NextPrime[k]];k]; Array[ lop,80] (* _Harvey P. Dale_, Sep 01 2022 *)
%o (PARI) a(n) = p=3; t=2^n; while(!isprime(1+p*t), p=nextprime(p+1)); p \\ _Colin Barker_, Jul 22 2014
%Y Cf. A098006, A134854.
%K nonn
%O 1,1
%A _T. D. Noe_, Nov 13 2007
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