A221737 - OEIS

A221737

Number of 2 X n arrays of occupancy after each element stays put or moves to some horizontal or antidiagonal neighbor, without move-in move-out left turns.

1, 17, 152, 1347, 11917, 105408, 932331, 8246429, 72939328, 645145427, 5706285509, 50471867376, 446421650827, 3948581668413, 34925047119456, 308910646572419, 2732302328399893, 24167104943016272, 213757077778269179

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OFFSET

1,2

COMMENTS

Row 2 of A221736.

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..210

FORMULA

Empirical: a(n) = 15*a(n-1) - 67*a(n-2) + 120*a(n-3) - 80*a(n-4) + 10*a(n-5) for n>6.

Empirical g.f.: x*(1 + 2*x - 36*x^2 + 86*x^3 - 64*x^4 + 12*x^5) / (1 - 15*x + 67*x^2 - 120*x^3 + 80*x^4 - 10*x^5). - Colin Barker, Aug 10 2018

EXAMPLE

Some solutions for n=3: