A157551 - OEIS

%I #6 Aug 01 2023 17:08:50

%S 1,9,114,3810,103185,2729181,69340908,1835068068,46949243445,

%T 1072699180795,22440539853666,442180822802082,8348531623530553,

%U 152424934237053765,2702148696449820840,46523455154624265192

%N Half the number of length n integer sequences with sum zero and sum of squares 722.

%H R. H. Hardin, <a href="/A157551/b157551.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,0,722)/2.

%K nonn

%O 2,2

%A _R. H. Hardin_, Mar 02 2009