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A060784
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Number of double tangents of order n.
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1
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0, 4, 0, 0, 28, 120, 324, 700, 1320, 2268, 3640, 5544, 8100, 11440, 15708, 21060, 27664, 35700, 45360, 56848, 70380, 86184, 104500, 125580, 149688, 177100, 208104, 243000, 282100, 325728, 374220, 427924, 487200, 552420, 623968
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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REFERENCES
| H. Brocard and T. Lemoyne: Courbes geometriques remarquables (courbes speciales) Planes et Gauches. Tome I, Paris: Albert Blanchard, 1967 [First publ. 1919]; see p. 375.
C.G.J. Jacobi, (Bericht ueber die zur Bekanntmachung geeigneten), Verhandlungen der Koenigl. Preuss. Akademie der Wiss. Berlin, 1850, p. 209, Jun 13, 1850.
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LINKS
| Harry J. Smith, Table of n, a(n) for n=0,...,1000
D. Ayala and R. Cavalieri, Counting bitangents with stable maps
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FORMULA
| n*(n-2)*(n-3)*(n+3)/2.
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PROG
| (PARI) { for (n=0, 1000, write("b060784.txt", n, " ", n*(n - 2)*(n - 3)*(n + 3)/2); ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Jul 11 2009]
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CROSSREFS
| Sequence in context: A019218 A125762 A196302 * A181204 A191417 A192057
Adjacent sequences: A060781 A060782 A060783 * A060785 A060786 A060787
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KEYWORD
| nonn
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AUTHOR
| Antreas P. Hatzipolakis (xpolakis(AT)otenet.gr), Apr 28 2001
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EXTENSIONS
| Jacobi reference from Wolfdieter Lang (wolfdieter.lang(AT)physik.uni-karlsruhe.de), Oct 09 2001
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