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Search: id:A157545
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| A157545 |
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Half the number of length n integer sequences with sum zero and sum of squares 338. |
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+0
1
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| 1, 9, 90, 1570, 32775, 596253, 10391500, 188323164, 3295910835, 51520770235, 737464758030, 9942564439314, 128439149539155, 1604475021960825, 19461485770566600, 229260099669952384, 2617537416673754961
(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,0,338)/2.
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CROSSREFS
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Sequence in context: A127769 A062815 A160569 this_sequence A157558 A157584 A128384
Adjacent sequences: A157542 A157543 A157544 this_sequence A157546 A157547 A157548
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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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