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%I #9 Jul 25 2021 02:34:22
%S 3,57,297,2189,25697,76721,123747,124443,132653,218207,244099,261023,
%T 267787,297059,304389,346623,366989,411971,462751,551057,596897,
%U 643181,647193,665967,671573,688143,701207,742197,748563,867003,872313,877331
%N Exactly 6 digits from {1,2,3,4,5,6,7,8,9} can precede a(n) to form a prime.
%C Finding 7, 8 and 9 preceding digits is a difficult job!
%e If a(n) = 57 then we find '1'57, '2'57, '4'57, '5'57, '7'57 and '8'57 to be primes.
%K nonn,base
%O 1,1
%A _Patrick De Geest_, May 15 1998
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