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A157551 Half the number of length n integer sequences with sum zero and sum of squares 722. 1
1, 9, 114, 3810, 103185, 2729181, 69340908, 1835068068, 46949243445, 1072699180795, 22440539853666, 442180822802082, 8348531623530553, 152424934237053765, 2702148696449820840, 46523455154624265192 (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,0,722)/2.

CROSSREFS

Sequence in context: A165224 A243676 A012116 * A157570 A223499 A157233

Adjacent sequences:  A157548 A157549 A157550 * A157552 A157553 A157554

KEYWORD

nonn

AUTHOR

R. H. Hardin Mar 02 2009

STATUS

approved

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Last modified December 22 09:44 EST 2014. Contains 252339 sequences.