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A167042
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Squares that remain squares when prefixed with a 7.
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3
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225, 5625, 22500, 562500, 2250000, 6125625, 19580625, 56250000, 225000000, 612562500, 1958062500, 2562890625, 5625000000, 22500000000, 51472265625, 61256250000, 195806250000, 256289062500, 562500000000, 2250000000000, 5147226562500, 6125625000000
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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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225 = 15^2 is a square, and becomes the square 7225 = 85^2 if prefixed with a 7.
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MATHEMATICA
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Select[Range[25*10^5]^2, IntegerQ[Sqrt[#+7*10^IntegerLength[#]]]&] (* Harvey P. Dale, Mar 02 2015 *)
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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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