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Search: id:A157593
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| A157593 |
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Half the number of length n integer sequences with sum zero and sum of squares 7442. |
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+0
1
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| 1, 9, 378, 37830, 3403815, 290684541, 23648592268, 2009304033948, 165069279069345, 12108533607540535, 813240975212887518, 51447280837022648370, 3118521194576489150631, 182797738828031587273965
(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,0,7442)/2.
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CROSSREFS
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Sequence in context: A162084 A051848 A157567 this_sequence A157602 A124042 A012191
Adjacent sequences: A157590 A157591 A157592 this_sequence A157594 A157595 A157596
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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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