A180789 - OEIS

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

%S 0,1,15,198,2282,19300,126861,670058,2997685,11539243,39660969,

%T 122371876,348412793,914595808,2264326584,5259342780,11692554312,

%U 24683815072,50403390786,98560661538,187881799209,345060981679,621482071341

%N Number of distinct solutions of sum{i=1..7}(x(2i-1)*x(2i)) = 1 (mod n), with x() only in 1..n-1

%C Column 7 of A180793

%H R. H. Hardin, <a href="/A180789/b180789.txt">Table of n, a(n) for n=1..183</a>

%e Solutions for sum of products of 7 1..2 pairs = 1 (mod 3) are

%e (1*1 + 1*1 + 1*1 + 1*1 + 1*1 + 1*1 + 1*1)

%e (1*1 + 1*1 + 1*1 + 1*1 + 1*1 + 1*1 + 2*2)

%e (1*1 + 1*1 + 1*1 + 1*1 + 1*2 + 1*2 + 1*2)

%e (1*1 + 1*1 + 1*1 + 1*1 + 1*1 + 2*2 + 2*2)

%e (1*1 + 1*1 + 1*1 + 1*1 + 2*2 + 2*2 + 2*2)

%e (1*1 + 1*1 + 1*1 + 1*2 + 1*2 + 1*2 + 2*2)

%e (1*1 + 1*1 + 1*1 + 2*2 + 2*2 + 2*2 + 2*2)

%e (1*1 + 1*1 + 1*2 + 1*2 + 1*2 + 2*2 + 2*2)

%e (1*1 + 1*1 + 2*2 + 2*2 + 2*2 + 2*2 + 2*2)

%e (1*1 + 1*2 + 1*2 + 1*2 + 1*2 + 1*2 + 1*2)

%e (1*1 + 1*2 + 1*2 + 1*2 + 2*2 + 2*2 + 2*2)

%e (1*1 + 2*2 + 2*2 + 2*2 + 2*2 + 2*2 + 2*2)

%e (1*2 + 1*2 + 1*2 + 1*2 + 1*2 + 1*2 + 2*2)

%e (1*2 + 1*2 + 1*2 + 2*2 + 2*2 + 2*2 + 2*2)

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

%K nonn

%O 1,3

%A _R. H. Hardin_ Sep 20 2010