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Search: id:A157542
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| A157542 |
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Half the number of length n integer sequences with sum zero and sum of squares 200. |
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+0
1
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| 1, 3, 42, 930, 17685, 265041, 3668483, 44840097, 529728300, 5955342987, 65311345275, 699155920398, 7170690213960, 69964606094670, 652763403442422, 5868431782886486, 51137730082075059, 433379839761592641
(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,0,200)/2.
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CROSSREFS
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Sequence in context: A003770 A097068 A092470 this_sequence A078601 A156108 A083402
Adjacent sequences: A157539 A157540 A157541 this_sequence A157543 A157544 A157545
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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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