A157599 - OEIS

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

%S 1,9,402,44230,4512465,423267831,37803628716,3527887213476,

%T 318332583745245,25647872392849575,1892012326768856754,

%U 131465592083214083058,8752726227773492626389,563521423775802944905950

%N Half the number of length n integer sequences with sum zero and sum of squares 8978.

%H R. H. Hardin, <a href="/A157599/b157599.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,0,8978)/2.

%K nonn

%O 2,2

%A _R. H. Hardin_ Mar 02 2009