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A198709 Number of n X n 0..3 arrays with values 0..3 introduced in row major order and no element equal to any horizontal or vertical neighbor 2

%I

%S 1,4,401,250031,851787199,15835552812749,1606578861528554441,

%T 889483369334451647489771,2687450673445984030296455830409

%N Number of n X n 0..3 arrays with values 0..3 introduced in row major order and no element equal to any horizontal or vertical neighbor

%C Diagonal of A198715

%H Jean-François Alcover, <a href="/A198709/b198709.txt">Table of n, a(n) for n = 1..16</a>

%e Some solutions with all values from 0 to 3 for n=4

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

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

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

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

%t A198715 = Import["https://oeis.org/A198715/b198715.txt", "Table"][[All, 2]];

%t a[n_] := A198715[[2 n^2 - 2 n + 1]];

%t Table[a[n], {n, 1, 16}] (* _Jean-François Alcover_, Sep 23 2019 *)

%K nonn

%O 1,2

%A _R. H. Hardin_ Oct 29 2011

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Last modified December 2 19:59 EST 2022. Contains 358510 sequences. (Running on oeis4.)