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Search: id:A001621
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| 0, 2, 12, 42, 110, 240, 462, 812, 1332, 2070, 3080, 4422, 6162, 8372, 11130, 14520, 18632, 23562, 29412, 36290, 44310, 53592, 64262, 76452, 90300, 105950, 123552, 143262, 165242, 189660, 216690
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OFFSET
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0,2
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COMMENT
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Number of integer sequences of length n+1 with sum zero and sum of absolute values 4. [From Ron Hardin (rhhardin(AT)att.net), Feb 22 2009]
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FORMULA
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G.f.:(-2*x*(x^2+x+1))/(x-1)^5 [From Maksym Voznyy (voznyy(AT)mail.ru), Jul 27 2009]
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MAPLE
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a:=n->add(n+add(binomial(n, 2), j=1..n), j=2..n):seq(a(n)/2, n=1..35); [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Aug 26 2008]
with(finance):seq(add(cashflows([k^3, k, 0], 0 ), k=0..n), n=0..45); # [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Dec 22 2008]
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MATHEMATICA
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a[n_]:=Sum[i+i^3, {i, 1, n}]; [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Dec 05 2008]
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CROSSREFS
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Equals 2 * A002817 and [A058919(n-1)-1]/2.
A092365 [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Aug 26 2008]
Sequence in context: A127725 A048014 A094702 this_sequence A055681 A111389 A013704
Adjacent sequences: A001618 A001619 A001620 this_sequence A001622 A001623 A001624
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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