A180829 - OEIS

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

%S 0,0,0,0,7,55,715,4260,25603,102717,408766,1258601,3851049,9814876,

%T 25170369,55987636,125991305,252719186,515720550,954717615,1803406803,

%U 3129204953,5559159252,9151697254,15453087022,24346596138,39398858317

%N Number of distinct solutions of sum{i=1..6}(x(2i-1)*x(2i)) = 1 (mod n), with x() only in 2..n-2

%C Column 6 of A180834

%H R. H. Hardin, <a href="/A180829/b180829.txt">Table of n, a(n) for n=1..183</a>

%e Solutions for sum of products of 6 2..3 pairs = 1 (mod 5) are

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

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

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

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

%K nonn

%O 1,5

%A _R. H. Hardin_ Sep 20 2010