A157553 - OEIS

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

%S 1,9,162,3010,100035,3757383,119414988,3493064772,95851672965,

%T 2417802179815,55917688232274,1207875284200806,25067626930769059,

%U 505877445756815265,9921228112937485800,188795923012791958280

%N Half the number of length n integer sequences with sum zero and sum of squares 882.

%H R. H. Hardin, <a href="/A157553/b157553.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,0,882)/2.

%K nonn

%O 2,2

%A _R. H. Hardin_ Mar 02 2009