A302987 - OEIS

%I #21 Apr 17 2018 06:59:56

%S 3,7,727,1595287,3773335151,53968982887,218662611751,373627441111,

%T 525882352087,612618285511

%N Primes p such that p+3 divides 3^p+3.

%C Conjecture: the sequence is finite.

%C Is this the same as the primes in A251862? - _Michel Marcus_, Apr 17 2018

%C a(11) > 10^12, if it exists. - _Giovanni Resta_, Apr 17 2018

%t Select[Prime[Range[10000]], Divisible[3^# + 3, # + 3] &] (* _Vincenzo Librandi_, Apr 17 2018 *)

%o (PARI) isok(p) = isprime(p) && (Mod(3,p+3)^p == Mod(-3,p+3)); \\ _Michel Marcus_, Apr 17 2018

%Y Cf. A000040, A000244, A302988.

%K nonn,hard,more

%O 1,1

%A _Alex Ratushnyak_, Apr 17 2018

%E a(4)-a(5) from _Michel Marcus_, Apr 17 2018

%E a(6)-a(10) from _Giovanni Resta_, Apr 17 2018