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Search: id:A157547
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| A157547 |
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Half the number of length n integer sequences with sum zero and sum of squares 450. |
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+0
1
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| 1, 3, 126, 2170, 37335, 921333, 21967484, 466292604, 9161931075, 164162481681, 2705726857350, 41747317681290, 619096670144225, 8923605271290360, 124998845674120920, 1699006653803990456, 22382667992161145863
(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,0,450)/2.
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CROSSREFS
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Sequence in context: A130614 A114877 A152859 this_sequence A157562 A157592 A159319
Adjacent sequences: A157544 A157545 A157546 this_sequence A157548 A157549 A157550
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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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