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Search: id:A015532
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| A015532 |
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a(n) = 4 a(n-1) + 7 a(n-2). |
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+0
1
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| 0, 1, 4, 23, 120, 641, 3404, 18103, 96240, 511681, 2720404, 14463383, 76896360, 408829121, 2173591004, 11556167863, 61439808480, 326652408961, 1736688295204, 9233320043543, 49090098240600, 260993633267201
(list; graph; listen)
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OFFSET
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0,3
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FORMULA
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O.g.f.: -x/(-1+4*x+7*x^2). a(n)=-7^n*(A^n-B^n)/(2sqrt(11)) where A=-1/(2+sqrt(11)) and B=1/(sqrt(11)-2) . - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 29 2008
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PROGRAM
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(Other) sage: [lucas_number1(n, 4, -7) for n in xrange(0, 21)]# [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Apr 23 2009]
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CROSSREFS
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Sequence in context: A082970 A017973 A124507 this_sequence A144465 A024050 A038723
Adjacent sequences: A015529 A015530 A015531 this_sequence A015533 A015534 A015535
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KEYWORD
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nonn,easy
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AUTHOR
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Olivier Gerard (olivier.gerard(AT)gmail.com)
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