cp's OEIS Frontend

A157007 Numbers k such that 2^k + 27 is prime.

%I A157007 #37 Nov 27 2023 10:29:30
%S A157007 1,2,4,5,8,10,13,14,16,40,41,44,86,110,125,133,134,145,154,184,194,
%T A157007 301,308,320,685,1001,1066,1496,1633,2005,2864,3241,6286,11585,12854,
%U A157007 16514,16540,19246,24538,28705,57644,65366,85276,89113,194854,266680,376790,478088
%N A157007 Numbers k such that 2^k + 27 is prime.
%C A157007 a(49) > 5*10^5. - _Robert Price_, Nov 06 2015
%H A157007 Henri Lifchitz and Renaud Lifchitz, <a href="http://www.primenumbers.net/prptop/searchform.php?form=2%5En%2B27">Search for 2^n+27</a>, PRP Top Records.
%e A157007 For k = 1, 2^1 + 27 = 29.
%e A157007 For k = 2, 2^2 + 27 = 31.
%e A157007 For k = 4, 2^4 + 27 = 43.
%t A157007 Delete[Union[Table[If[PrimeQ[2^n + 27], n, 0], {n, 1, 2000}]], 1]
%t A157007 Select[Range[5000],PrimeQ[2^#+27]&] (* _Harvey P. Dale_, Mar 24 2011 *)
%o A157007 (PARI) for(n=1, 1e3, if(isprime(2^n+3^3), print1(n", "))) \\ _Altug Alkan_, Oct 04 2015
%o A157007 (Magma) [n: n in [0..1000] | IsPrime(2^n+27)]; // _Vincenzo Librandi_, Oct 05 2015
%Y A157007 Cf. A057733, A094076, A104071, A123250.
%Y A157007 Cf. A019434 (primes 2^k+1), A057732 (2^k+3), A059242 (2^k+5), A057195 (2^k+7), A057196 (2^k+9), A102633 (2^k+11), A102634 (2^k+13), A057197 (2^k+15), A057200 (2^k+17), A057221 (2^k+19), A057201 (2^k+21), A057203 (2^k+23), A157006 (2^k+25), this sequence (2^k+27), A156982 (2^k+29), A247952 (2^k+31), A247953 (2^k+33), A220077 (2^k+35).
%K A157007 nonn
%O A157007 1,2
%A A157007 Edwin Dyke (ed.dyke(AT)btinternet.com), Feb 20 2009
%E A157007 More terms from _Harvey P. Dale_, Mar 24 2011
%E A157007 a(33)-a(42) from _Robert Price_, Oct 04 2015
%E A157007 a(43)-a(47) discovered by _Henri Lifchitz_ and Lelio R Paula from Lifchitz link by _Robert Price_, Oct 04 2015
%E A157007 a(48) from _Robert Price_, Nov 06 2015