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Search: id:A132584
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| A132584 |
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Sequence allows us to find X values of the equation: X(X + 1) - 5*Y^2 = 0. |
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+0
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| 0, 4, 80, 1444, 25920, 465124, 8346320, 149768644, 2687489280, 48225038404, 865363202000, 15528312597604, 278644263554880, 5000068431390244, 89722587501469520, 1610006506595061124, 28890394531209630720
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OFFSET
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0,2
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FORMULA
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a(0)=0, a(1)=4 and a(n)=18*a(n-1) - a(n-2) + 8.
a(n)=-(1/2)+(1/4)*[9-4*sqrt(5)]^n+(1/4)*[9+4*sqrt(5)]^n, with n>=0 [From Paolo P. Lava (ppl(AT)spl.at), Oct 07 2008]
a(n) = (A023039(n) - 1)/2 [From Max Alekseyev (maxale(AT)gmail.com), Nov 13 2009]
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CROSSREFS
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Cf. A007654.
Sequence in context: A054322 A114488 A055787 this_sequence A012127 A057875 A012824
Adjacent sequences: A132581 A132582 A132583 this_sequence A132585 A132586 A132587
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KEYWORD
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nonn,new
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AUTHOR
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Mohamed Bouhamida (bhmd95(AT)yahoo.fr), Nov 14 2007
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EXTENSIONS
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More terms from Max Alekseyev (maxale(AT)gmail.com), Nov 13 2009
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