A157594 - OEIS

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

%S 1,9,198,29790,4026105,406849401,33869423679,2526809359383,

%T 185063876167860,12982668662313075,884404700588788401,

%U 58698938381426781945,3731136219706944217260,225710021147180429934270

%N Half the number of length n integer sequences with sum zero and sum of squares 7688.

%H R. H. Hardin, <a href="/A157594/b157594.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,0,7688)/2.

%K nonn

%O 2,2

%A _R. H. Hardin_ Mar 02 2009