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A156842
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529n^2 - 746n + 263.
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4
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46, 887, 2786, 5743, 9758, 14831, 20962, 28151, 36398, 45703, 56066, 67487, 79966, 93503, 108098, 123751, 140462, 158231, 177058, 196943, 217886, 239887, 262946, 287063, 312238, 338471, 365762, 394111, 423518, 453983, 485506, 518087
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OFFSET
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1,1
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COMMENTS
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The identity (279841*n^2-394634*n+139128)^2-(529*n^2-746*n+263)*(12167*n-8579)^2=1 can be written as A156844(n)^2-a(n)*A156845(n)^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*(-46-749*x-263*x^2)/(x-1)^3.
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MATHEMATICA
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LinearRecurrence[{3, -3, 1}, {46, 887, 2786}, 40]
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PROG
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(Magma) I:=[46, 887, 2786]; [n le 3 select I[n] else 3*Self(n-1)-3*Self(n-2)+1*Self(n-3): n in [1..40]];
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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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EXTENSIONS
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STATUS
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approved
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