A216989 - OEIS

A216989

Number of city-block distance 1, pressure limit 2 movements in an nX6 array with each element moving exactly one horizontally or vertically, no element acquiring more than two neighbors, and without 2-loops

%I #4 Sep 21 2012 17:02:59

%S 0,2346,1435808,886416182,524266454832,307860650044792,

%T 180328865345987360,105557191885030726384,61776749660998923874410,

%U 36152465383268281809542282,21156493983680665465727818196

%N Number of city-block distance 1, pressure limit 2 movements in an nX6 array with each element moving exactly one horizontally or vertically, no element acquiring more than two neighbors, and without 2-loops

%C Column 6 of A216991

%H R. H. Hardin, <a href="/A216989/b216989.txt">Table of n, a(n) for n = 1..210</a>

%e Some solutions for n=3 (movement: 0=n 1=e 2=s 3=w)

%e ..2..2..1..2..1..2....2..2..2..2..3..3....2..2..1..2..3..3....2..2..2..3..2..2

%e ..2..2..3..3..2..3....2..3..1..2..0..0....2..2..3..2..2..2....2..1..1..0..3..3

%e ..1..1..0..0..3..3....1..0..0..1..1..0....1..1..0..3..3..3....1..0..3..3..3..0

%K nonn

%O 1,2

%A _R. H. Hardin_ Sep 21 2012