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A167717
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Squares that become a prime number when prefixed with a 2.
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1
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9, 81, 441, 729, 1089, 1521, 6561, 8649, 16641, 19881, 33489, 53361, 56169, 71289, 74529, 84681, 88209, 103041, 168921, 173889, 251001, 257049, 263169, 269361, 288369, 301401, 314721, 335241, 370881, 423801, 463761, 514089, 549081, 558009
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OFFSET
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1,1
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COMMENTS
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LINKS
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MATHEMATICA
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Select[Range[1, 500, 2]^2, PrimeQ[FromDigits[Join[{2}, IntegerDigits[#]]]] &](* G. C. Greubel, Jun 21 2016 *)
Select[Range[800]^2, PrimeQ[2*10^IntegerLength[#]+#]&] (* Harvey P. Dale, Oct 23 2022 *)
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CROSSREFS
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KEYWORD
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base,nonn
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AUTHOR
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STATUS
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approved
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