%I #7 Nov 22 2024 16:32:02
%S 7,71,73,79,733,7333,79999,733333,799999,71111111,799999999,
%T 79999999999,79999999999999999999999999,
%U 79999999999999999999999999999999999999999999999999
%N Primes of the form identical digits preceded by a 7.
%H Vincenzo Librandi, <a href="/A090155/b090155.txt">Table of n, a(n) for n = 1..24</a>
%t Select[ FromDigits /@ Flatten[ Table[ PadRight[{7}, i, # ] & /@ {1, 2, 3, 4, 5, 6, 7, 8, 9}, {i, 2, 50}], 1], PrimeQ[ # ] &]
%t Select[FromDigits/@Flatten[Table[PadRight[{7},i,#]&/@{1,3,7,9},{i,50}],1],PrimeQ[#]&]//Union (* _Harvey P. Dale_, Nov 22 2024 *)
%K nonn,base,changed
%O 1,1
%A _Robert G. Wilson v_, Nov 22 2003