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Search: id:A055809
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| 1, 15, 32, 56, 88, 129, 180, 242, 316, 403, 504, 620, 752, 901, 1068, 1254, 1460, 1687, 1936, 2208, 2504, 2825, 3172, 3546, 3948, 4379, 4840, 5332, 5856, 6413, 7004, 7630, 8292, 8991, 9728, 10504, 11320, 12177, 13076
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OFFSET
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4,2
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COMMENT
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If Y_i (i=1,2,3,4) are 2-blocks of an n-set X then, for n>=8, a(n-2) is the number of (n-3)-subsets of X intersecting each Y_i (i=1,2,3,4). - Milan R. Janjic (agnus(AT)blic.net), Nov 09 2007
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LINKS
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Milan Janjic, Two Enumerative Functions
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FORMULA
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For n>4, a(n) = n(n^2+3n-22)/6.
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CROSSREFS
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Sequence in context: A041448 A061047 A098848 this_sequence A007256 A112147 A089966
Adjacent sequences: A055806 A055807 A055808 this_sequence A055810 A055811 A055812
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KEYWORD
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nonn
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AUTHOR
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Clark Kimberling (ck6(AT)evansville.edu), May 28 2000
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