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A117662
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n(n-1)(n-2)(n+3)/12.
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3
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0, 0, 0, 3, 14, 40, 90, 175, 308, 504, 780, 1155, 1650, 2288, 3094, 4095, 5320, 6800, 8568, 10659, 13110, 15960, 19250, 23023, 27324, 32200, 37700, 43875, 50778, 58464, 66990, 76415, 86800, 98208, 110704, 124355, 139230, 155400, 172938, 191919
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,4
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COMMENTS
| Also, the number of external intersections of the diagonals of a general n-gon = (A176145) - (A000332). - Michel Lagneau Michel Lagneau (mn.lagneau2(AT)orange.fr), Apr 21 2010
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FORMULA
| G.f.: x^3*(3-x)/(1-x)^5. [Colin Barker, Jan 31 2012]
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MAPLE
| seq(n*(n-1)*(n-2)*(n+3)/12, n=0..40);
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CROSSREFS
| Sequence in context: A034130 A005701 A050297 * A196236 A104905 A055650
Adjacent sequences: A117659 A117660 A117661 * A117663 A117664 A117665
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KEYWORD
| nonn,easy
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AUTHOR
| Roger Bagula (rlbagulatftn(AT)yahoo.com), Apr 11 2006
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EXTENSIONS
| Edited by N. J. A. Sloane (njas(AT)research.att.com), Apr 23 2006
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