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A157568
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Half the number of length n integer sequences with sum zero and sum of squares 2592.
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1
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1, 3, 54, 6710, 552975, 42285705, 2331601391, 101037868356, 4170874974720, 169800684016755, 6716524310262195, 256753303252023825, 9424676123728329646, 331044899193112524525, 11129765080736905244370, 360217055543666912443944
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internal format)
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OFFSET
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2,2
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LINKS
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R. H. 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,0,2592)/2.
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CROSSREFS
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Sequence in context: A158103 A174579 A171739 * A156911 A214006 A154604
Adjacent sequences: A157565 A157566 A157567 * A157569 A157570 A157571
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KEYWORD
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nonn
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AUTHOR
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R. H. Hardin Mar 02 2009
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STATUS
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approved
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