A090153 Primes of the form identical digits preceded by a 5.

5, 53, 59, 577, 599, 5333, 59999, 511111, 599999, 59999999, 577777777, 59999999999, 5111111111111, 53333333333333, 59999999999999, 577777777777777, 5111111111111111, 577777777777777777

Offset: 1

Author

Robert G. Wilson v, Nov 22 2003

Keywords

• nonn
• base

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..43

Programs

Mathematica

Select[ FromDigits /@ Flatten[ Table[ PadRight[{5}, i, # ] & /@ {1, 2, 3, 4, 5, 6, 7, 8, 9}, {i, 2, 24}], 1], PrimeQ[ # ] &]
Join[{5},Select[Flatten[Table[FromDigits[PadRight[{5},n,k]],{n,2,20},{k,{1,3,7,9}}]],PrimeQ]] (* Harvey P. Dale, May 31 2020 *)