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A157541
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Half the number of length n integer sequences with sum zero and sum of squares 162.
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1
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1, 3, 54, 610, 7575, 124005, 1721692, 21584676, 254430555, 2752913955, 27276416970, 252510790038, 2245919946361, 19423497389310, 163254969718200, 1331429118674408, 10524020807274019, 80607360684092143, 599129356328684230
(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,0,162)/2.
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CROSSREFS
| Sequence in context: A045481 A174782 A119294 * A065102 A003776 A157550
Adjacent sequences: A157538 A157539 A157540 * A157542 A157543 A157544
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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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