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402, 1604, 3606, 6408, 10010, 14412, 19614, 25616, 32418, 40020, 48422, 57624, 67626, 78428, 90030, 102432, 115634, 129636, 144438, 160040, 176442, 193644, 211646, 230448, 250050, 270452, 291654, 313656, 336458, 360060, 384462, 409664
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OFFSET
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1,1
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COMMENTS
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The identity (400*n+1)^2-(400*n^2+2*n)*(20)^2=1 can be written as A158313(n)^2-a(n)*(20)^2=1.
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LINKS
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FORMULA
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a(n) = 3*a(n-1) -3*a(n-2) +a(n-3).
G.f.: x*(402+398*x)/(1-x)^3.
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MATHEMATICA
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LinearRecurrence[{3, -3, 1}, {402, 1604, 3606}, 50]
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PROG
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(Magma) I:=[402, 1604, 3606]; [n le 3 select I[n] else 3*Self(n-1)-3*Self(n-2)+1*Self(n-3): n in [1..50]];
(PARI) a(n) = 400*n^2 + 2*n.
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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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