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A005605
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a(n) = a(n-1) + (-1)^(n-1) * a(n-2)^2.
(Formerly M0176)
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1
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0, 1, 1, 2, 1, 5, 4, 29, 13, 854, 685, 730001, 260776, 532901720777, 464897598601, 283984244007552571082330, 67854466822576053925129, 80647050844541158378200602801460469923692154029
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,4
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REFERENCES
| J. Mestel, Archimedeans Problems Drive 1977, Eureka, 39 (1978), 38-40.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
| Reinhard Zumkeller, Table of n, a(n) for n = 0..25
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FORMULA
| For odd n, a(n) = floor(c^(2^((n-5)/2))) where c = 5.40649051189479721671529024151000148043062587729806430849172463824709059699198634362266484243.... - Gerald McGarvey (gerald.mcgarvey(AT)comcast.net), Dec 08 2004
The alternating version of this sequence, b(n) = (-1)^(n-1)*a(n) = 0,1,-1,2,-1,5,-4,29,-13,..., satisfies b(n) = b(n-2)^2 - b(n-1). - Franklin T. Adams-Watters (FrankTAW(AT)Netscape.net), Feb 27 2007
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PROG
| (Haskell)
a005605 n = a005605_list !! n
a005605_list = 0 : 1 : zipWith (+) (tail a005605_list)
(zipWith (*) (cycle [-1, 1]) (map (^ 2) $ a005605_list))
-- Reinhard Zumkeller, Feb 16 2012
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CROSSREFS
| Sequence in context: A079285 A124660 A141485 * A145882 A111785 A021468
Adjacent sequences: A005602 A005603 A005604 * A005606 A005607 A005608
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KEYWORD
| nonn,easy,nice,changed
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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