%I #3 Mar 31 2012 12:35:46

%S 0,0,0,0,5,13,103,302,1182,2676,7472,14368,32620,55157,110783,172932,

%T 315241,457366,783739,1088297,1750273,2335589,3624725,4656872,6991039,

%U 8758150,12682152,15651854,22182704,26463796,37062084,43858102,59401343

%N Number of distinct solutions of sum{i=1..4}(x(2i-1)*x(2i)) = 1 (mod n), with x() only in 2..n-2

%C Column 4 of A180834

%H R. H. Hardin, <a href="/A180827/b180827.txt">Table of n, a(n) for n=1..376</a>

%e Solutions for sum of products of 4 2..4 pairs = 1 (mod 6) are

%e (2*2 + 2*2 + 2*4 + 3*3) (2*2 + 2*3 + 2*3 + 3*3) (2*2 + 2*3 + 3*3 + 3*4)

%e (2*2 + 2*4 + 3*3 + 4*4) (2*2 + 3*3 + 3*3 + 3*3) (2*2 + 3*3 + 3*4 + 3*4)

%e (2*3 + 2*3 + 3*3 + 4*4) (2*3 + 2*4 + 2*4 + 3*3) (2*3 + 3*3 + 3*4 + 4*4)

%e (2*4 + 2*4 + 3*3 + 3*4) (2*4 + 3*3 + 4*4 + 4*4) (3*3 + 3*3 + 3*3 + 4*4)

%e (3*3 + 3*4 + 3*4 + 4*4)

%K nonn

%O 1,5

%A _R. H. Hardin_ Sep 20 2010