A056710 Near-repdigit primes such that all digits are equal except for an end-digit.

113, 199, 211, 223, 227, 229, 233, 277, 311, 331, 337, 433, 443, 449, 499, 557, 577, 599, 661, 677, 733, 773, 811, 877, 881, 883, 887, 911, 977, 991, 997, 1117, 1777, 1999, 2111, 2221, 2333, 2777, 2999, 3331, 4111, 4441, 4447, 4999, 5333, 5557, 6661, 7333, 8111, 8887, 8999

Offset: 1

Author

Robert G. Wilson v, Aug 10 2000

Keywords

• nonn
• base

Links

• Giovanni Resta, Table of n, a(n) for n = 1..496 (terms < 10^1000)

Programs

Mathematica

Select[ Range[ 101, 10^4, 2 ], PrimeQ[ # ] && (Length[ Union[ Take[ RealDigits[ # ][ [ 1 ] ], {1, -2} ] ] ] == 1 || Length[ Union[ Take[ RealDigits[ # ][ [ 1 ] ], {2, -1} ] ] ] == 1) & ]
dig[n_] := Sort@Select[Flatten@Table[{d*10^(n - 1) + e*(10^(n - 1) - 1)/9, e + 10 d*(10^(n-1)- 1)/9}, {e, {1,3,7,9}}, {d, Delete[Range@9, e]}], PrimeQ]; Join @@ dig /@ Range[3, 100] (* terms < 10^100, Giovanni Resta, Apr 08 2013 *)

Extensions

Four missing terms added by Giovanni Resta, Apr 07 2013