A060522 Number of 4 X n grids of black and white cells, no 3 of same color vertically or horizontally contiguous.

10, 100, 378, 2030, 9484, 46746, 225654, 1098136, 5327258, 25875154, 125619088, 609970274, 2961628194, 14380186660, 69822244298, 339019686614, 1646096608476, 7992561729954, 38807580840854, 188428757462264, 914908750899146, 4442305123352810, 21569445781449640

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 degree-5 relation for this one.

Links

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

Sean A. Irvine, Java program (github)

Formula

Empirical: a(n)=3*a(n-1)+12*a(n-2)+a(n-3)-58*a(n-4)-115*a(n-5)+83*a(n-6)+312*a(n-7)+120*a(n-8)-336*a(n-9)-348*a(n-10)+420*a(n-11)+104*a(n-12)-194*a(n-13)+43*a(n-14)+35*a(n-15)-42*a(n-16)-3*a(n-17)+14*a(n-18)-a(n-19)-a(n-20) - 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