%I #4 Mar 31 2012 12:35:46
%S 0,2,7,12,24,31,59,74,111,121,202,208,323,310,454,484,695,597,957,874,
%T 1183,1125,1665,1448,2070,1823,2439,2304,3273,2524,3980,3464,4367,
%U 3982,5470,4440,6692,5515,7110,6488,9056,6728,10422,8592,10542,9666,13554
%N Number of distinct solutions of sum{i=1..2}(x(2i-1)*x(2i)) = 1 (mod n), with x() in 0..n-1
%C Column 2 of A180813
%H R. H. Hardin, <a href="/A180804/b180804.txt">Table of n, a(n) for n=1..999</a>
%e Solutions for sum of products of 2 0..2 pairs = 1 (mod 3) are
%e (0*0 + 1*1) (0*0 + 2*2) (0*1 + 1*1) (0*1 + 2*2) (0*2 + 1*1) (0*2 + 2*2)
%e (1*2 + 1*2)
%K nonn
%O 1,2
%A _R. H. Hardin_, suggested by _Max Alekseyev_ in the Sequence Fans Mailing List, Sep 20 2010