A087091 - OEIS

%I #12 Dec 27 2019 11:50:56

%S 1,4,10,16,19,31,34,43,55,58,61,70,73,79,85,94,100,118,148,154,160,

%T 175,196,199,211,214,223,226,229,238,253,274,313,340,424,430,469,499,

%U 508,529,538,541,550,565,640,658,673,706,724,760,763,781

%N Numbers k such that p = k^2 + k + 41 and p - 2 are twin primes.

%H Amiram Eldar, <a href="/A087091/b087091.txt">Table of n, a(n) for n = 1..10000</a>

%e 4 is in the sequence because 61 = 4^2 + 4 + 41 and 59 are twin primes.

%t Select[Range[10^3], And @@ PrimeQ[#^2 + # + {39, 41}] &] (* _Amiram Eldar_, Dec 27 2019 *)

%o (PARI) isok(n) = isprime(n^2+n+41) && isprime(n^2+n+39); \\ _Michel Marcus_, Oct 03 2013

%Y Cf. A007634, A087090.

%K nonn

%O 1,2

%A _Zak Seidov_, Aug 08 2003