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A157515
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a(n) = 1000*n - 20.
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3
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980, 1980, 2980, 3980, 4980, 5980, 6980, 7980, 8980, 9980, 10980, 11980, 12980, 13980, 14980, 15980, 16980, 17980, 18980, 19980, 20980, 21980, 22980, 23980, 24980, 25980, 26980, 27980, 28980, 29980, 30980, 31980, 32980, 33980, 34980
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OFFSET
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1,1
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COMMENTS
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The identity (5000*n^2 - 200*n + 1)^2 - (25*n^2 - n)*(1000*n - 20)^2 = 1 can be written as A157516(n)^2 - A157514(n)*a(n)^2 = 1 (see also the second part of the comment at A157514). - Vincenzo Librandi, Jan 26 2012
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LINKS
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FORMULA
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MATHEMATICA
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PROG
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(Magma) I:=[980, 1980]; [n le 2 select I[n] else 2*Self(n-1)-Self(n-2): n in [1..50]]; // Vincenzo Librandi, Jan 26 2012
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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