A157557 - OEIS

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

%S 1,3,222,7810,245715,7887621,271336828,9598223664,323149486005,

%T 9653120522639,265199107509930,6875831133411318,170878889034103705,

%U 4105071237469192095,95749849725794169816,2169082695217727013712

%N Half the number of length n integer sequences with sum zero and sum of squares 1250.

%H R. H. Hardin, <a href="/A157557/b157557.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,0,1250)/2.

%K nonn

%O 2,2

%A _R. H. Hardin_ Mar 02 2009