Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.
%I #12 Jun 22 2022 15:42:33
%S 19,49999,599999,1799999999999999999,2099999999999999999999,
%T 289999999999999999999999999999
%N Primes of the form k followed by k 9's.
%C Corresponding k, which cannot be multiples of 3, are in A174352. The next term has 176 digits, too large to include here. - _Rick L. Shepherd_, Mar 22 2010
%t Select[Table[FromDigits[PadRight[{k},k+1,9]],{k,200}],PrimeQ] (* _Harvey P. Dale_, Jun 22 2022 *)
%o (PARI) lista(nn) = for(k=1, nn, if(ispseudoprime(q=k*10^(k-1)-1), print1(q, ", "))); \\ _Jinyuan Wang_, Mar 24 2020
%Y Cf. A141311, A145852.
%Y Cf. A174352. - _Rick L. Shepherd_, Mar 22 2010
%K nonn,base
%O 1,1
%A _Lekraj Beedassy_, Oct 21 2008
%E a(2) was 4999; corrected by _Rick L. Shepherd_, Mar 22 2010