A157563 - OEIS

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

%S 1,9,198,9930,447345,19373781,801643164,34613610228,1445069106945,

%T 53870000270295,1838679236576886,59112727361906010,

%U 1820954720583759943,54244177130219463765,1568969312068377795960,44074283494841644862536

%N Half the number of length n integer sequences with sum zero and sum of squares 1922.

%H R. H. Hardin, <a href="/A157563/b157563.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,0,1922)/2.

%K nonn

%O 2,2

%A _R. H. Hardin_ Mar 02 2009