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A068989
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Squares which when reversed are primes (ignore leading zeros).
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3
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16, 196, 361, 784, 1024, 1369, 1444, 1600, 1681, 3844, 7225, 7921, 9025, 9409, 11236, 14161, 18496, 19321, 19600, 36100, 37249, 38416, 70756, 73441, 75076, 76729, 78400, 78961, 97969, 99856, 102400, 105625, 107584, 109561, 111556, 112225
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OFFSET
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1,1
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LINKS
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EXAMPLE
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40^2 = 1600. Reversing the digits we get 0061, which is the prime 61 padded with leading zeroes. Hence 1600 is in the sequence.
41^2 = 1681. Reversing the digits we get 1861, which is a prime. Hence 1681 is in the sequence.
42^2 = 1764. Reversing the digits we get 4671 = 3^3 * 173. So 1764 is not in the sequence.
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MATHEMATICA
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Do[s = i^2; If[PrimeQ[FromDigits[Reverse[IntegerDigits[s]]]], Print[s]], {i, 1, 10^2}] (* Pe *)
Select[Range[100]^2, PrimeQ[FromDigits[Reverse[IntegerDigits[#]]]] &] (* Alonso del Arte, Jan 07 2018 *)
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PROG
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(PARI) isok(n) = issquare(n) && isprime(fromdigits(Vecrev(digits(n)))); \\ Michel Marcus, Jan 07 2018
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CROSSREFS
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Cf. primes whose reversal is a square, A007488; numbers n such that n^2 reversed is a prime, A059007.
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KEYWORD
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easy,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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