A157556 - OEIS

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

%S 1,3,18,3010,166725,8371713,307008163,8869151172,244109996040,

%T 6625340217595,174712060895757,4452494561526960,108958868923534266,

%U 2551477805087525055,57187304932168982070,1233918981730653994884

%N Half the number of length n integer sequences with sum zero and sum of squares 1152.

%H R. H. Hardin, <a href="/A157556/b157556.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,0,1152)/2.

%K nonn

%O 2,2

%A _R. H. Hardin_ Mar 02 2009