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A157540
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Half the number of length n integer sequences with sum zero and sum of squares 128.
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1
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1, 3, 6, 430, 8775, 114681, 1213471, 11685663, 110201400, 997307245, 8767514811, 75092781699, 615909156954, 4807634283375, 35885733707970, 258099905201634, 1799253706774203, 12198525957520155, 80576646822300850, 518883888358457370
(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,0,128)/2.
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CROSSREFS
| Sequence in context: A083149 A068375 A126297 * A179267 A171928 A034879
Adjacent sequences: A157537 A157538 A157539 * A157541 A157542 A157543
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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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