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%I #14 Mar 29 2015 23:00:22
%S 2,3,7,337,32353,7727255227,23523352753755575323
%N a(1) = 2; for n>1, a(n) is the least prime with all prime digits which is == 1 (mod a(n-1)).
%C a(7) > 2*10^19. - _Robert G. Wilson v_, Nov 27 2004
%C a(8) > 2*10^32. - _Jon E. Schoenfield_, Mar 29 2015
%e a(4) = 337, a(5) = 32353 == 1 (mod 337).
%t a[1] = 2; a[n_] := a[n] = Block[{k = 1, p = a[n - 1]}, While[ !PrimeQ[k*p + 1] || Union[ Join[{2, 3, 5, 7}, IntegerDigits[k*p + 1]]] != {2, 3, 5, 7}, k++ ]; k*p + 1]; Table[ a[n], {n, 6}] (* _Robert G. Wilson v_, Nov 27 2004 *)
%K base,nonn
%O 1,1
%A _Amarnath Murthy_, Nov 25 2004
%E a(6) from _Robert G. Wilson v_, Nov 27 2004
%E a(7) from _Jon E. Schoenfield_, Mar 29 2015
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