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A157549
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Half the number of length n integer sequences with sum zero and sum of squares 578.
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1
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1, 3, 102, 2730, 73965, 1747893, 39747932, 941571576, 21552984495, 440593787755, 8246912787894, 145396398912414, 2456171567279885, 40123597587869565, 636426718791995640, 9804070912688974376, 146378210616014587821
(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,0,578)/2.
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CROSSREFS
| Sequence in context: A108220 A130733 A037062 * A157566 A157600 A139908
Adjacent sequences: A157546 A157547 A157548 * A157550 A157551 A157552
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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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