|
%I #6 Mar 31 2012 12:35:55
%S 1,1,3,7,21,45,121,261,723,1723,5087,13091,38641,101993,297423,800187,
%T 2324961,6378601,18544345,51670725,150172263,422922591,1228542913,
%U 3488055573,10134018375,28962183951,84203226523,241924870591
%N Number of strings of n numbers x(i) in -1..1 with sums of x(i) and of x(i)*x(i+1) both zero
%C Column 1 of A183944
%H R. H. Hardin, <a href="/A183936/b183936.txt">Table of n, a(n) for n = 1..200</a>
%e All solutions for n=4
%e ..1....0....0...-1...-1....1....0
%e ..0....0....1....0....0....0...-1
%e .-1....0....0....0....1....0....0
%e ..0....0...-1....1....0...-1....1
%K nonn
%O 1,3
%A _R. H. Hardin_ Jan 08 2011
|
