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Search: id:A157565
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| A157565 |
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Half the number of length n integer sequences with sum zero and sum of squares 2178. |
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+0
1
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| 1, 3, 198, 9310, 376485, 22631679, 1141749532, 52484724372, 2266995222285, 89935056097975, 3267564223225962, 110915350947910158, 3617265650971040159, 114705568549182973950, 3535047653641613917560, 105710505247924746059104
(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,0,2178)/2.
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CROSSREFS
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Sequence in context: A093978 A101382 A000724 this_sequence A157598 A023310 A054701
Adjacent sequences: A157562 A157563 A157564 this_sequence A157566 A157567 A157568
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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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