A180797 - OEIS

%I #4 Mar 31 2012 12:35:46

%S 1,12,87,549,2338,9383,28783,85956,213618,518268,1100399,2370275,

%T 4457359,8595967,15130785,26913348,43848123,74308434,114423976,

%U 184270107,274414305,419987334,601573248,905711494,1247825148,1806542438

%N Number of distinct solutions of sum{i=1..5}(x(2i-1)*x(2i)) = 0 (mod n), with x() in 0..n-1

%C Column 5 of A180803

%H R. H. Hardin, <a href="/A180797/b180797.txt">Table of n, a(n) for n=1..249</a>

%e Solutions for sum of products of 5 0..1 pairs = 0 (mod 2) are

%e (0*0 + 0*0 + 0*0 + 0*0 + 0*0) (0*0 + 0*0 + 0*0 + 0*0 + 0*1)

%e (0*0 + 0*0 + 0*0 + 0*1 + 0*1) (0*0 + 0*0 + 0*0 + 1*1 + 1*1)

%e (0*0 + 0*0 + 0*1 + 0*1 + 0*1) (0*0 + 0*0 + 0*1 + 1*1 + 1*1)

%e (0*0 + 0*1 + 0*1 + 0*1 + 0*1) (0*0 + 0*1 + 0*1 + 1*1 + 1*1)

%e (0*0 + 1*1 + 1*1 + 1*1 + 1*1) (0*1 + 0*1 + 0*1 + 0*1 + 0*1)

%e (0*1 + 0*1 + 0*1 + 1*1 + 1*1) (0*1 + 1*1 + 1*1 + 1*1 + 1*1)

%K nonn

%O 1,2

%A _R. H. Hardin_, suggested by _Max Alekseyev_ in the Sequence Fans Mailing List, Sep 20 2010