A068254 1/4 the number of colorings of an n X n square array with 4 colors.

1, 21, 2403, 1500183, 5110723191, 95013316876491, 9639473169171326643, 5336900216006709884938623, 16124704040675904181778734982451, 265865038636937159336134567410478299051

Offset: 1

Author

R. H. Hardin, Feb 24 2002

Keywords

• nonn

Links

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

Crossrefs

Main diagonal of A222444.

Cf. A068239-A068305, A000332, A002417, A027441, A182368, A182406.

Programs

Mathematica

A222444 = Cases[Import["https://oeis.org/A222444/b222444.txt", "Table"], {, }][[All, 2]];
a[n_] := A222444[[2 n^2 - 2 n + 1]];
Table[a[n], {n, 1, 16}] (* Jean-François Alcover, Sep 23 2019 *)

Extensions

a(9)-a(10) from Alois P. Heinz, Apr 27 2012