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Search: id:A092286
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| 0, 6, 16, 31, 52, 80, 116, 161, 216, 282, 360, 451, 556, 676, 812, 965, 1136, 1326, 1536, 1767, 2020, 2296, 2596, 2921, 3272, 3650, 4056, 4491, 4956, 5452, 5980, 6541, 7136, 7766, 8432, 9135, 9876, 10656, 11476, 12337, 13240, 14186, 15176
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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If X is an n-set and Y a fixed (n-4)-subset of X then a(n-4) is equal to the number of 3-subsets of X intersecting Y. - Milan R. Janjic (agnus(AT)blic.net), Aug 15 2007
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LINKS
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Milan Janjic, Two Enumerative Functions
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FORMULA
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a(n) = A084938(n+3, n) = Sum_{k=0..3} A090238(3, k)*binomial(n, k).
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MAPLE
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a:=n->sum((j-1)*j/2, j=4..n): seq(a(n), n=3..45); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Dec 02 2006
seq(binomial(n, 3)-4, n=4..46); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jan 13 2007
with (combinat):a[2]:=1:for n from 2 to 50 do a[n]:=binomial(n+2, n)+a[n-1] od: seq(a[n], n=1..43); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Mar 17 2008
a:=n->sum(binomial(j, 2), j=4..n): seq(a(n), n=3..45); # [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Dec 31 2008]
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CROSSREFS
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Cf. A084938 A090238.
Sequence in context: A102214 A115007 A005891 this_sequence A108182 A097118 A134465
Adjacent sequences: A092283 A092284 A092285 this_sequence A092287 A092288 A092289
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KEYWORD
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easy,nonn
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AUTHOR
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DELEHAM Philippe (kolotoko(AT)wanadoo.fr), Jan 30 2004
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