cp's OEIS Frontend

A225304 Number of nX3 -1,1 arrays such that the sum over i=1..n,j=1..3 of i*x(i,j) is zero and rows are nondecreasing (ways to put 3 thrusters pointing east or west at each of n positions 1..n distance from the hinge of a south-pointing gate without turning the gate).

%I A225304 #7 Jun 02 2025 08:31:41
%S A225304 0,0,6,16,0,0,474,1576,0,0,64700,228876,0,0,10659862,38869960,0,0,
%T A225304 1941920508,7211917300,0,0,376790653888,1416598649968,0,0,
%U A225304 76344225166632,289560610889154,0,0,15965033749025502,60953934482465398,0,0
%N A225304 Number of nX3 -1,1 arrays such that the sum over i=1..n,j=1..3 of i*x(i,j) is zero and rows are nondecreasing (ways to put 3 thrusters pointing east or west at each of n positions 1..n distance from the hinge of a south-pointing gate without turning the gate).
%C A225304 Column 3 of A225310
%H A225304 R. H. Hardin, <a href="/A225304/b225304.txt">Table of n, a(n) for n = 1..210</a>
%e A225304 Some solutions for n=4
%e A225304 .-1.-1..1...-1.-1.-1....1..1..1...-1.-1.-1...-1.-1..1...-1.-1.-1...-1..1..1
%e A225304 .-1.-1.-1...-1..1..1...-1.-1.-1....1..1..1....1..1..1...-1.-1.-1...-1..1..1
%e A225304 .-1..1..1...-1.-1..1...-1.-1.-1....1..1..1...-1.-1.-1...-1.-1..1....1..1..1
%e A225304 .-1..1..1...-1..1..1....1..1..1...-1.-1.-1...-1..1..1....1..1..1...-1.-1.-1
%K A225304 nonn
%O A225304 1,3
%A A225304 _R. H. Hardin_ May 05 2013