

A060522


Number of 4 X n grids of black and white cells, no 3 of same color vertically or horizontally contiguous.


2



10, 100, 378, 2030, 9484, 46746, 225654, 1098136, 5327258, 25875154, 125619088, 609970274, 2961628194, 14380186660, 69822244298
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OFFSET

1,1


COMMENTS

The 1 X n, 2 X n, 3 X n versions satisfied recurrence relations of degrees 2, 3, 4 respectively, but I have done quite a lot of LLL work and failed to find a degree5 relation for this one.


LINKS

R. H. Hardin, Table of n, a(n) for n = 1..212


FORMULA

Empirical: a(n)=3*a(n1)+12*a(n2)+a(n3)58*a(n4)115*a(n5)+83*a(n6)+312*a(n7)+120*a(n8)336*a(n9)348*a(n10)+420*a(n11)+104*a(n12)194*a(n13)+43*a(n14)+35*a(n15)42*a(n16)3*a(n17)+14*a(n18)a(n19)a(n20)  R. H. Hardin, Jan 01 2012


CROSSREFS

Sequence in context: A208416 A208024 A207804 * A086115 A209652 A207072
Adjacent sequences: A060519 A060520 A060521 * A060523 A060524 A060525


KEYWORD

nonn


AUTHOR

Tom Womack (tom(AT)womack.net)


STATUS

approved



