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Search: id:A157595
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| A157595 |
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Half the number of length n integer sequences with sum zero and sum of squares 7938. |
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+0
1
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| 1, 9, 486, 26230, 2658825, 303936255, 29022562044, 2546840675268, 209628417451815, 15863225333113455, 1100628488842991790, 71323826984704710078, 4440654868991991482287, 268844012960749492143465
(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,0,7938)/2.
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CROSSREFS
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Sequence in context: A061175 A166879 A128947 this_sequence A042415 A112910 A102909
Adjacent sequences: A157592 A157593 A157594 this_sequence A157596 A157597 A157598
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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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