A198906 - OEIS

A198906

T(n,k) = number of n X k 0..4 arrays with values 0..4 introduced in row major order and no element equal to any horizontal or vertical neighbor.

1, 1, 1, 2, 4, 2, 5, 33, 33, 5, 15, 380, 1211, 380, 15, 51, 4801, 50384, 50384, 4801, 51, 187, 62004, 2125425, 6907736, 2125425, 62004, 187, 715, 804833, 89793204, 948656912, 948656912, 89793204, 804833, 715, 2795, 10459180, 3794115705

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OFFSET

1,4

COMMENTS

Number of colorings of the grid graph P_n X P_k using a maximum of 5 colors up to permutation of the colors. - Andrew Howroyd, Jun 26 2017

LINKS

Andrew Howroyd, Table of n, a(n) for n = 1..378 (terms 1..127 from R. H. Hardin)

EXAMPLE

Table starts

.....1..........1...............2....................5

.....1..........4..............33..................380

.....2.........33............1211................50384

.....5........380...........50384..............6907736

....15.......4801.........2125425............948656912

....51......62004........89793204.........130292546801

...187.....804833......3794115705.......17895005957823

...715...10459180....160319061892.....2457786852894234

..2795..135958401...6774239755817...337564362706067534

.11051.1767426404.286243775060868.46362726246946052884

...

Some solutions with values 0 to 4 for n=6, k=4:

..0..1..0..1....0..1..0..1....0..1..0..1....0..1..0..1....0..1..0..1

..1..0..1..0....1..0..1..0....1..0..1..0....1..0..1..0....1..0..1..0

..0..1..0..2....0..1..0..2....0..1..0..2....0..1..0..2....0..1..0..2

..2..0..2..0....2..0..3..0....2..0..2..3....2..0..1..0....2..0..1..3

..3..2..1..4....0..1..0..4....0..4..0..2....3..2..4..3....0..3..4..2

..2..4..2..1....2..4..3..1....1..3..1..4....1..0..1..2....4..0..1..4

CROSSREFS

Columns 1-7 are A007581(n-2), A198900, A198901, A198902, A198903, A198904, A198905.

Main diagonal is A198899.

Cf. A207997 (3 colorings), A198715 (4 colorings), A222144 (labeled 5 colorings), A198982 (6 colorings), A198723 (7 colorings), A198914 (8 colorings), A207868 (unlimited).

Sequence in context: A085843 A198715 A216663 * A198982 A198723 A198914

Adjacent sequences: A198903 A198904 A198905 * A198907 A198908 A198909

KEYWORD

nonn,tabl

AUTHOR

R. H. Hardin, Oct 31 2011

STATUS

approved