A174180 - OEIS

%I #14 Sep 08 2022 08:45:51

%S 1,3,9,17,19,27,351,813,869,1387

%N Numbers n>0 such that 10^n+2^n+1 is prime.

%C Terms greater than 351 yield probable primes. Next term > 10000. - _Vaclav Kotesovec_, Apr 30 2014

%t Select[Range[1,1000],PrimeQ[10^#+2^#+1]&] (* _Vaclav Kotesovec_, Apr 30 2014 *)

%o (Magma) [n: n in [1..800] | IsPrime(10^n+2^n+1) ]

%K nonn,more

%O 1,2

%A _Vincenzo Librandi_, Mar 11 2010

%E a(8)-a(10) from _Vaclav Kotesovec_, Apr 30 2014