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Search: id:A157580
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| A157580 |
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Half the number of length n integer sequences with sum zero and sum of squares 4608. |
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+0
1
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| 1, 3, 18, 11970, 1334085, 133955073, 9824277155, 567625941444, 31246085767560, 1696086845812315, 89452573267087437, 4559354532659814420, 223147765159835078290, 10450853058701142231795, 468478402281324084911670
(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,0,4608)/2.
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CROSSREFS
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Sequence in context: A157556 A057133 A001999 this_sequence A101293 A078096 A139429
Adjacent sequences: A157577 A157578 A157579 this_sequence A157581 A157582 A157583
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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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