%I #4 Mar 31 2012 12:35:25

%S 1,3,102,2730,73965,1747893,39747932,941571576,21552984495,

%T 440593787755,8246912787894,145396398912414,2456171567279885,

%U 40123597587869565,636426718791995640,9804070912688974376,146378210616014587821

%N Half the number of length n integer sequences with sum zero and sum of squares 578.

%H R. H. Hardin, <a href="/A157549/b157549.txt">Table of n, a(n) for n=2..50</a>

%F [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,0,578)/2.

%K nonn

%O 2,2

%A _R. H. Hardin_ Mar 02 2009