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Search: id:A157561
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| A157561 |
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Half the number of length n integer sequences with sum zero and sum of squares 1682. |
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+0
1
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| 1, 3, 186, 8710, 366285, 14870583, 574288652, 23199133896, 906030228645, 31596296548135, 1008864177035154, 30341990819899122, 874376529563919655, 24366254356588107705, 659305049442735042120, 17325808811806633829408
(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,0,1682)/2.
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CROSSREFS
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Sequence in context: A053291 A042779 A103503 this_sequence A157590 A157236 A058856
Adjacent sequences: A157558 A157559 A157560 this_sequence A157562 A157563 A157564
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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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