A090157 Primes of the form identical digits preceded by a 9.
97, 911, 977, 97777, 911111, 97777777777777777777, 911111111111111111111, 97777777777777777777777777777, 911111111111111111111111111111111111111111
Offset: 1
Links
- Vincenzo Librandi, Table of n, a(n) for n = 1..21
Programs
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Mathematica
Select[ FromDigits /@ Flatten[ Table[ PadRight[{9}, i, # ] & /@ {1, 2, 3, 4, 5, 6, 7, 8, 9}, {i, 2, 50}], 1], PrimeQ[ # ] &] Select[Union[Flatten[Table[FromDigits[PadRight[{9},n,d]],{n,2,50},{d,{1,7}}]]],PrimeQ] (* Harvey P. Dale, Jun 27 2020 *)
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