A090147 Primes of the form identical digits followed by a 7.

7, 17, 37, 47, 67, 97, 227, 337, 557, 887, 997, 1117, 4447, 5557, 8887, 11117, 333337, 555557, 666667, 888887, 11111117, 66666667, 222222227, 666666667, 888888887, 4444444447, 5555555557, 66666666667, 888888888887, 222222222222227

Offset

1,1

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..68

Mathematica

Select[ FromDigits /@ Flatten[ Table[ PadLeft[{7}, i, # ] & /@ {1, 2, 3, 4, 5, 6, 7, 8, 9}, {i, 2, 18}], 1], PrimeQ[ # ] &]
Select[Union[Flatten[Table[FromDigits[PadLeft[{7}, n, d]], {n, 15}, {d, 9}]]], PrimeQ] (* Harvey P. Dale, Nov 15 2020 *)

Crossrefs

Sequence in context: A106095 A153319 A030432 * A348560 A338030 A211476

Adjacent sequences: A090144 A090145 A090146 * A090148 A090149 A090150

Keyword

nonn,base

Author

Robert G. Wilson v, Nov 22 2003

Status

approved