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Search: id:A157551
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| A157551 |
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Half the number of length n integer sequences with sum zero and sum of squares 722. |
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+0
1
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| 1, 9, 114, 3810, 103185, 2729181, 69340908, 1835068068, 46949243445, 1072699180795, 22440539853666, 442180822802082, 8348531623530553, 152424934237053765, 2702148696449820840, 46523455154624265192
(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,0,722)/2.
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CROSSREFS
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Sequence in context: A155624 A165224 A012116 this_sequence A157570 A157233 A083305
Adjacent sequences: A157548 A157549 A157550 this_sequence A157552 A157553 A157554
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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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