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.

1, 4, 401, 250031, 851787199, 15835552812749, 1606578861528554441, 889483369334451647489771, 2687450673445984030296455830409

Offset

1,2

Comments

Diagonal of A198715

Links

Jean-François Alcover, Table of n, a(n) for n = 1..16

Example

Some solutions with all values from 0 to 3 for n=4
..0..1..0..1....0..1..0..2....0..1..0..1....0..1..0..2....0..1..2..0
..1..2..1..3....1..2..1..3....1..0..2..3....2..3..2..3....1..0..3..1
..2..1..3..2....2..1..3..2....2..3..1..2....1..2..0..1....0..3..1..2
..1..3..1..0....1..2..0..1....3..0..2..1....2..0..3..0....2..1..2..3

Mathematica

A198715 = Import["https://oeis.org/A198715/b198715.txt", "Table"][[All, 2]];
a[n_] := A198715[[2 n^2 - 2 n + 1]];
Table[a[n], {n, 1, 16}] (* Jean-François Alcover, Sep 23 2019 *)

Crossrefs

Sequence in context: A158111 A259049 A280791 * A326209 A396671 A287965

Adjacent sequences: A198706 A198707 A198708 * A198710 A198711 A198712

Keyword

nonn

Author

R. H. Hardin, Oct 29 2011

Status

approved