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A056710
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Near-repdigit primes such that all digits are equal except for an end-digit.
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3
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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
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OFFSET
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1,1
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LINKS
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MATHEMATICA
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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 *)
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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