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A157548
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Half the number of length n integer sequences with sum zero and sum of squares 512.
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1
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1, 3, 6, 1710, 70215, 1835001, 38831135, 747772191, 14106580920, 255318883105, 4489013718651, 76895304533697, 1261399140060514, 19692099463166235, 293975822555447490, 4228706577830551202, 58957940194082852859
(list; graph; refs; listen; history; internal format)
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OFFSET
| 2,2
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LINKS
| R. H. Hardin, Table of n, a(n) for n=2..50
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FORMULA
| [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,0,512)/2.
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CROSSREFS
| Sequence in context: A034879 A113588 A071106 * A134901 A157564 A122182
Adjacent sequences: A157545 A157546 A157547 * A157549 A157550 A157551
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KEYWORD
| nonn
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AUTHOR
| R. H. Hardin (rhhardin(AT)att.net) Mar 02 2009
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