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A157543
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Half the number of length n integer sequences with sum zero and sum of squares 242.
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1
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1, 3, 66, 1330, 19815, 310023, 4512844, 69146820, 1023450345, 13538157655, 163977086526, 1870633964706, 20447484311345, 216134818489905, 2218284360150120, 22111545640638832, 213615563307370209
(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,0,242)/2.
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CROSSREFS
| Sequence in context: A091470 A028567 A003359 * A157984 A187547 A157554
Adjacent sequences: A157540 A157541 A157542 * A157544 A157545 A157546
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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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