%I #35 Sep 08 2022 08:46:18

%S 71,6271,20971519999,3696558092582911,71248353479884799,

%T 36607563614276605181951,66626319770601443076406771711,

%U 46716685589841799771959773105092594214371327,3855174423960385883723562689229267550261846474751

%N Primes of the form n^2*2^n - 1.

%F a(n) = A000040(A058781(n)).

%e a(1) = 3^2*2^3 - 1 = 71 is prime where 3 = A058781(1).

%e a(2) = 7^2*2^7 - 1 = 6271 is prime where 7 = A058781(2).

%t Select[Table[n^2 2^n - 1, {n, 0, 150}], PrimeQ] (* _Vincenzo Librandi_, Jan 20 2017 *)

%o (Magma) [a: n in [1..45] | IsPrime(a) where a is n^2*2^n-1];

%o (PARI) select(ispseudoprime, apply(n->n^2*2^n - 1, [1..200])) \\ _Charles R Greathouse IV_, Jan 20 2017

%Y Cf. A058781.

%K nonn

%O 1,1

%A _Juri-Stepan Gerasimov_, Jan 17 2017