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A069684
Primes with either no internal digits or all internal digits are 9.
18
2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 191, 193, 197, 199, 293, 397, 491, 499, 593, 599, 691, 797, 991, 997, 1993, 1997, 1999, 2999, 4993, 4999, 6991, 6997, 7993, 8999, 19991, 19993, 19997, 49991, 49993, 49999
OFFSET
1,1
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..252 (* All terms with less than 500 digits. *)
MATHEMATICA
Join[Prime[Range[25]], Select[Flatten[Table[FromDigits[Join[{d1}, PadRight[{}, n, 9], {d2}]], {n, 150}, {d1, 9}, {d2, {1, 3, 7, 9}}]], PrimeQ]] (* Harvey P. Dale, Nov 10 2024 *)
KEYWORD
nonn,base,changed
AUTHOR
Amarnath Murthy, Apr 06 2002
EXTENSIONS
Corrected by Ray Chandler, Nov 24 2003
Offset corrected and name changed by Arkadiusz Wesolowski, Sep 07 2011
STATUS
approved