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A157576 Half the number of length n integer sequences with sum zero and sum of squares 3872. 1
1, 3, 66, 14630, 1446495, 105717843, 6111518987, 323657828739, 16777260176400, 835056998169955, 40377792647031081, 1902059925519314067, 85804943707548960986, 3683698658760163764945, 151229533594426205964390 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,2

LINKS

R. H. Hardin, Table of n, a(n) for n=2..50

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,0,3872)/2.

CROSSREFS

Sequence in context: A157554 A185053 A165655 * A105443 A065425 A096482

Adjacent sequences:  A157573 A157574 A157575 * A157577 A157578 A157579

KEYWORD

nonn

AUTHOR

R. H. Hardin Mar 02 2009

STATUS

approved

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Last modified September 27 19:04 EDT 2020. Contains 337388 sequences. (Running on oeis4.)