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A153050
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Six-digit squares that are concatenation of two 3-digit primes.
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2
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101761, 113569, 127449, 131769, 137641, 149769, 167281, 199809, 349281, 439569, 463761, 491401, 641601, 683929, 797449
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OFFSET
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1,1
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COMMENTS
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There are exactly 15 such numbers.
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LINKS
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MATHEMATICA
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c = 0; t = 1000; re = Sort[Reap[Do[If[PrimeQ[p], Do[If[PrimeQ[q], r = p*t + q; s = Sqrt[r]; If[s == Floor[s], c++; Sow[r]]], {q, 101, 999, 2}]], {p, 101, 999, 2}]][[2, 1]]]
concatpQ[n_]:=Module[{idn=IntegerDigits[n], a, b}, a=FromDigits[Take[idn, 3]]; b=FromDigits[Take[idn, -3]]; IntegerLength[a]==IntegerLength[b]==3 && PrimeQ[a]&&PrimeQ[b]]; Select[Range[316, 1000]^2, concatpQ] (* Harvey P. Dale, Mar 09 2012 *)
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CROSSREFS
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KEYWORD
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fini,full,nonn,base
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AUTHOR
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STATUS
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approved
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