1,1

a(13) > 10^5. - Robert Price, Mar 26 2015

Select[Range[5000], PrimeQ[(10^# - 2 # + 1)] &] (* Vincenzo Librandi, Oct 05 2012 *)

(Magma) /* The code gives only the terms up to 354: */ [n: n in [1..600] | IsPrime(10^n-2*n+1) ];

(PARI) is(n)=ispseudoprime(10^n-2*n+1) \\ Charles R Greathouse IV, Feb 20 2017

Cf. A173837, A110065, A110066, A110067.

Sequence in context: A000660 A148325 A281594 * A298367 A025274 A132833

Adjacent sequences: A174173 A174174 A174175 * A174177 A174178 A174179

nonn,more

Vincenzo Librandi, Mar 11 2010

a(8)-a(10) from Vincenzo Librandi, Oct 05 2012

a(11)-a(12) from Robert Price, Mar 26 2015

approved