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A157534
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Half the number of length n integer sequences with sum zero and sum of squares 8.
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1
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1, 3, 6, 30, 135, 441, 1183, 2871, 6660, 15070, 33231, 70863, 145236, 285390, 537930, 974746, 1703043, 2878101, 4719220, 7529340, 11718861, 17834223, 26591841, 38918025, 55995550, 79317576, 110749653, 152600581, 207702930, 279504060
(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,0,8)/2.
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CROSSREFS
| Sequence in context: A136946 A125521 A090932 * A133799 A088436 A088506
Adjacent sequences: A157531 A157532 A157533 * A157535 A157536 A157537
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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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