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 A167717 Squares that become a prime number when prefixed with a 2. 1
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Subsequence of squares of A032665. - Michel Marcus, Jun 21 2016 LINKS G. C. Greubel, Table of n, a(n) for n = 1..10000 MATHEMATICA 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 *) CROSSREFS Cf. A032665. Sequence in context: A221963 A207742 A207719 * A208079 A223719 A270295 Adjacent sequences: A167714 A167715 A167716 * A167718 A167719 A167720 KEYWORD base,nonn AUTHOR Claudio Meller, Nov 10 2009 STATUS approved

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Last modified April 19 08:45 EDT 2024. Contains 371782 sequences. (Running on oeis4.)