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A157538
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Half the number of length n integer sequences with sum zero and sum of squares 72.
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1
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1, 3, 18, 210, 2565, 32193, 299299, 2161092, 14903940, 101124595, 666560697, 4246100664, 25977358680, 152079371640, 852145833870, 4596664464916, 24033240110143, 122242188808411, 605721155611160, 2925464857935060
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OFFSET
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2,2
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LINKS
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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,0,72)/2.
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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