%I #11 Feb 16 2025 08:32:58
%S 3,160,812
%N Numbers n such that (initial n digits of decimal expansion of 1/243)-1 is prime.
%H Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/243.html">243</a>.
%t Do[ If[ PrimeQ[ Floor[10^n/243 - 1]], Print[n]], {n, 8000}] (* _Robert G. Wilson v_, Jun 10 2005 *)
%o (PARI) for(n=1,999,if(isprime(floor(1/243*10^n)-1),print1(n",")))
%Y Cf. A021247.
%K more,nonn,base,bref,dumb,changed
%O 1,1
%A _Jason Earls_, Jun 07 2005