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A095661
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Fifth column (m=4) of (1,3)-Pascal triangle A095660.
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13
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3, 13, 35, 75, 140, 238, 378, 570, 825, 1155, 1573, 2093, 2730, 3500, 4420, 5508, 6783, 8265, 9975, 11935, 14168, 16698, 19550, 22750, 26325, 30303, 34713, 39585, 44950, 50840, 57288, 64328, 71995, 80325, 89355, 99123, 109668, 121030, 133250, 146370
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OFFSET
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0,1
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COMMENTS
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If Y is a 3-subset of an n-set X then, for n>=6, a(n-6) is the number of 4-subsets of X having at most one element in common with Y. - Milan Janjic, Nov 23 2007
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LINKS
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FORMULA
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G.f.: (3-2*x)/(1-x)^5.
a(n)= (n+12)*binomial(n+3, 3)/4 = 3*b(n)-2*b(n-1), with b(n):=binomial(n+4, 4); cf. A000332.
a(n) = sum_{k=1..n} ( sum_{i=1..k} i*(n-k+3) ), with offset 1. - Wesley Ivan Hurt, Sep 25 2013
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MAPLE
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MATHEMATICA
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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