A157541 - OEIS

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

%S 1,3,54,610,7575,124005,1721692,21584676,254430555,2752913955,

%T 27276416970,252510790038,2245919946361,19423497389310,

%U 163254969718200,1331429118674408,10524020807274019,80607360684092143,599129356328684230

%N Half the number of length n integer sequences with sum zero and sum of squares 162.

%H R. H. Hardin, <a href="/A157541/b157541.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,0,162)/2.

%K nonn

%O 2,2

%A _R. H. Hardin_ Mar 02 2009