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A081017
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Lucas(4n+1)-1, or 5*Fibonacci(2n)*Fibonacci(2n+1).
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1
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0, 10, 75, 520, 3570, 24475, 167760, 1149850, 7881195, 54018520, 370248450, 2537720635, 17393796000, 119218851370, 817138163595, 5600748293800, 38388099893010, 263115950957275, 1803423556807920, 12360848946698170
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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REFERENCES
| Hugh C. Williams, Edouard Lucas and Primality Testing, John Wiley and Sons, 1998, p. 75
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FORMULA
| a(n) = 8a(n-1)-8a(n-2)+a(n-3)
a(n)=-1+(1/2)*{[(7/2)-(3/2)*sqrt(5)]^n+[(7/2)+(3/2)*sqrt(5)]^n}+(1/2)*sqrt(5)*{[(7/2)+(3/2)*sqrt(5)]^n -[(7/2)-(3/2)*sqrt(5)]^n}, with n>=0 [From Paolo P. Lava (paoloplava(AT)gmail.com), Dec 01 2008]
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MAPLE
| with(combinat): option remember: if n=0 then RETURN(2) fi: if n=1 then RETURN(1) fi: luc(n-1)+luc(n-2): end: for n from 0 to 25 do printf(`%d, `, luc(4*n+1)-1) od:
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CROSSREFS
| Cf. A000045 (Fibonacci numbers), A000032 (Lucas numbers).
Sequence in context: A111998 A026935 A110127 * A025015 A049392 A136869
Adjacent sequences: A081014 A081015 A081016 * A081018 A081019 A081020
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KEYWORD
| nonn,easy
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AUTHOR
| R. K. Guy (rkg(AT)cpsc.ucalgary.ca), Mar 01, 2003
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EXTENSIONS
| More terms and Maple code from James A. Sellers (sellersj(AT)math.psu.edu), Mar 03, 2003
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