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Search: id:A157576
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| A157576 |
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Half the number of length n integer sequences with sum zero and sum of squares 3872. |
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+0
1
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| 1, 3, 66, 14630, 1446495, 105717843, 6111518987, 323657828739, 16777260176400, 835056998169955, 40377792647031081, 1902059925519314067, 85804943707548960986, 3683698658760163764945, 151229533594426205964390
(list; graph; listen)
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OFFSET
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2,2
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LINKS
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Ron Hardin, Table of n, a(n) for n=2..50
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FORMULA
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[cache enabling] count(n,s,ss)->count(n,t,tt) where t=s mod n, q=(t-s)/n, tt=ss+2*q*s+n*q^2; count(n,t,tt)=sum[i^2<=tt]{ count(n-1,t-i,tt-i^2) }. a(n)=count(n,0,3872)/2.
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CROSSREFS
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Sequence in context: A157984 A157554 A165655 this_sequence A105443 A065425 A096482
Adjacent sequences: A157573 A157574 A157575 this_sequence A157577 A157578 A157579
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KEYWORD
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nonn
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AUTHOR
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Ron Hardin (rhhardin(AT)att.net) Mar 02 2009
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