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A086781
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a(n) is the number of nonzero terms in the expansion of (x-y) * (x^2-y^2) * (x^3-y^3) * ... * (x^n-y^n).
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7
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1, 2, 4, 6, 7, 12, 14, 18, 25, 32, 36, 42, 53, 68, 64, 84, 97, 108, 126, 146, 161, 170, 192, 208, 229, 246, 274, 300, 333, 348, 372, 400, 427, 468, 492, 526, 561, 602, 626, 644, 691, 736, 772, 826, 869, 902, 930, 974, 1017, 1062, 1120, 1184, 1223, 1262, 1314, 1374, 1419, 1468, 1518, 1586, 1663, 1718, 1778, 1834, 1899, 1954, 2018
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OFFSET
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0,2
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COMMENTS
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LINKS
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MAPLE
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a:=proc(n) options operator, arrow: nops(expand(product(x^j-y^j, j=1..n))) end proc: seq(a(n), n=0..50); # Emeric Deutsch, Jan 01 2008
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MATHEMATICA
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Table[Length[Expand[Times@@(x^Range[n]-1)]], {n, 50}] (* Harvey P. Dale, Mar 01 2012 *)
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PROG
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(PARI) a(n)=#select(w->w, Vec(prod(k=1, n, 1-'x^k))); \\ Joerg Arndt, Apr 12 2017
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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Yuval Dekel (dekelyuval(AT)hotmail.com), Aug 03 2003
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EXTENSIONS
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STATUS
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approved
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