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A011920
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a(n) = b(n)*(b(n)+1) = b(n) + ... + c(n), where b(n) = A011916(n), c(n) = A011918(n).
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2
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12, 1980, 378840, 73419192, 14241916260, 2762844014580, 535977297450672, 103976830083273840, 20170969020163148220, 3913064012542622257452, 759114247456742016195720, 147264250942490855924510760
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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REFERENCES
| Mario VELUCCHI "Seeing couples" in Recreational and Educational Computing, to appear 1997.
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LINKS
| Index to sequences with linear recurrences with constant coefficients, signature (209,-2926,2926,-209,1). [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 15 2010]
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FORMULA
| a(n)= +209*a(n-1) -2926*a(n-2) +2926*a(n-3) -209*a(n-4) +a(n-5). G.f.: -12*x*(1-44*x+11*x^2)/ ((x-1) * (x^2-14*x+1) * (x^2-194*x+1)). [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 15 2010]
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MAPLE
| Contribution from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 15 2010: (Start)
A011922 := proc(n) (2+sqrt(1+((((2+sqrt(3))^(2*n)-(2-sqrt(3))^(2*n))^2)/4)))/3 ; expand(%) ; simplify(%) ; end proc:
A011916 := proc(n) ((A011922(n)-1)+sqrt(3*A011922(n)^2-4*A011922(n)+1))/2 ; end proc:
A011920 := proc(n) A011916(n)*(A011916(n)+1) ; end proc:
seq(A011920(n), n=1..20) ; (End)
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CROSSREFS
| Sequence in context: A104009 A015028 A167745 * A204622 A004823 A009063
Adjacent sequences: A011917 A011918 A011919 * A011921 A011922 A011923
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KEYWORD
| nonn,easy
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AUTHOR
| Mario Velucchi (mathchess(AT)velucchi.it)
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EXTENSIONS
| More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 15 2010
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