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Search: id:A157590
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| A157590 |
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Half the number of length n integer sequences with sum zero and sum of squares 6728. |
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+0
1
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| 1, 3, 186, 26130, 3296565, 312282243, 24263695547, 1693530847881, 116031418602660, 7614709044887230, 485263665372726339, 30129597082995141381, 1791597506670518058876, 101387984322685789268190
(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,0,6728)/2.
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CROSSREFS
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Sequence in context: A042779 A103503 A157561 this_sequence A157236 A058856 A158469
Adjacent sequences: A157587 A157588 A157589 this_sequence A157591 A157592 A157593
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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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