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 A157572 Half the number of length n integer sequences with sum zero and sum of squares 3200. 1

%I

%S 1,3,42,13330,1149525,68923281,3762973571,184036492377,8678968080840,

%T 390210773279547,17118756925603575,733096379424490302,

%U 30076017737894907870,1173815703627064565445,43806372065182513944702

%N Half the number of length n integer sequences with sum zero and sum of squares 3200.

%H R. H. Hardin, <a href="/A157572/b157572.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,0,3200)/2.

%K nonn

%O 2,2

%A _R. H. Hardin_ Mar 02 2009

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Last modified August 11 10:15 EDT 2022. Contains 356065 sequences. (Running on oeis4.)