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Search: id:A157581
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| A157581 |
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Half the number of length n integer sequences with sum zero and sum of squares 4802. |
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+0
1
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| 1, 15, 390, 21010, 1806015, 123582921, 7932838172, 541388995092, 35637846633315, 2098170095389555, 113237331813959034, 5754386605886291022, 280189305372079613419, 13193562175797681608910, 603200922513642478421880
(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,0,4802)/2.
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CROSSREFS
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Sequence in context: A164323 A129615 A069990 this_sequence A143001 A034675 A069431
Adjacent sequences: A157578 A157579 A157580 this_sequence A157582 A157583 A157584
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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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