A216990 - OEIS

A216990

Number of city-block distance 1, pressure limit 2 movements in an nX7 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 17:03:42

%S 0,12578,24673352,49491906456,94821314531592,180328865345987360,

%T 342045101062468307160,648338338792898616469226,

%U 1228659499592627438742733120,2328285492440707317251867198066

%N Number of city-block distance 1, pressure limit 2 movements in an nX7 array with each element moving exactly one horizontally or vertically, no element acquiring more than two neighbors, and without 2-loops

%C Column 7 of A216991

%H R. H. Hardin, <a href="/A216990/b216990.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..2..2..3..1..2....2..2..2..2..1..2..3....2..2..2..2..3..2..3

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

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

%K nonn

%O 1,2

%A _R. H. Hardin_ Sep 21 2012