Finding large numbers that are probably prime

? probprime(n, a=2) = Mod(a,n)^(n-1) == Mod(1,n)
? x = 0948609348698406983409580934859034509834095809348509834905809345
%36 = 948609348698406983409580934859034509834095809348509834905809345
? for(i=0,100,if(probprime(x+2*i,2),print(i)))
27
? p = x + 2*27
%37 = 948609348698406983409580934859034509834095809348509834905809399
? probprime(p,3)
%39 = 1