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 A216984 Number of city-block distance 1, pressure limit 2 movements in an n X n array with each element moving exactly one horizontally or vertically, no element acquiring more than two neighbors, and without 2-loops 1

%I

%S 0,2,264,280900,2891592224,307860650044792,342045101062468307160,

%T 3979259269110908593906417328,485168384985330726560602698774047840,

%U 620116995791586597194849424436942942331423388

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

%C Diagonal of A216991

%H R. H. Hardin, <a href="/A216984/b216984.txt">Table of n, a(n) for n = 1..11</a>

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

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

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

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

%K nonn

%O 1,2

%A _R. H. Hardin_ Sep 21 2012

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Last modified March 26 05:43 EDT 2019. Contains 321481 sequences. (Running on oeis4.)