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Search: id:A157546
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| A157546 |
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Half the number of length n integer sequences with sum zero and sum of squares 392. |
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+0
1
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| 1, 9, 54, 1290, 47385, 1080891, 19941831, 335927439, 5541820740, 87714576070, 1349748111657, 20228679068676, 290345411571852, 3966279413712840, 51810189395306490, 652108043960695984, 7955418278826810531
(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,0,392)/2.
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CROSSREFS
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Sequence in context: A037704 A093847 A157539 this_sequence A157560 A157588 A058849
Adjacent sequences: A157543 A157544 A157545 this_sequence A157547 A157548 A157549
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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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