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Search: id:A090728
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| A090728 |
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a(n) = 20a(n-1) - a(n-2), starting with a(0) = 2 and a(1) = 20. |
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+0
2
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| 2, 20, 398, 7940, 158402, 3160100, 63043598, 1257711860, 25091193602, 500566160180, 9986232009998, 199224074039780, 3974495248785602, 79290680901672260, 1581839122784659598, 31557491774791519700
(list; graph; listen)
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OFFSET
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0,1
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LINKS
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Tanya Khovanova, Recursive Sequences
Index entries for recurrences a(n) = k*a(n - 1) +/- a(n - 2)
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FORMULA
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a(n) = p^n + q^n, where p = 10 + 3sqrt(11) and q = 10 - 3sqrt(11). - Tanya Khovanova (tanyakh(AT)yahoo.com), Feb 06 2007
G.f.: (2-20*x)/(1-20*x+x^2). [From Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Nov 02 2008]
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MATHEMATICA
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a[0] = 2; a[1] = 20; a[n_] := 20a[n - 1] - a[n - 2]; Table[ a[n], {n, 0, 15}] (from Robert G. Wilson v Jan 30 2004)
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PROGRAM
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sage: [lucas_number2(n, 20, 1) for n in xrange(0, 20)] - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jun 27 2008
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CROSSREFS
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Cf. A080959, A037035, A054877.
Cf. A001085 .
Sequence in context: A084948 A009236 A078698 this_sequence A090309 A002116 A058346
Adjacent sequences: A090725 A090726 A090727 this_sequence A090729 A090730 A090731
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KEYWORD
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easy,nonn
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AUTHOR
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Nikolay V. Kosinov (kosinov(AT)unitron.com.ua), Jan 18 2004
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EXTENSIONS
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More terms from Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 30 2004
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