%I A157590
%S A157590 1,3,186,26130,3296565,312282243,24263695547,1693530847881,
%T A157590 116031418602660,7614709044887230,485263665372726339,
%U A157590 30129597082995141381,1791597506670518058876,101387984322685789268190
%N A157590 Half the number of length n integer sequences with sum zero and sum of 
               squares 6728.
%H A157590 Ron Hardin, <a href="b157590.txt">Table of n, a(n) for n=2..50</a>
%F A157590 [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,0,6728)/2.
%Y A157590 Sequence in context: A042779 A103503 A157561 this_sequence A157236 A058856 
               A158469
%Y A157590 Adjacent sequences: A157587 A157588 A157589 this_sequence A157591 A157592 
               A157593
%K A157590 nonn
%O A157590 2,2
%A A157590 Ron Hardin (rhhardin(AT)att.net) Mar 02 2009