A206537 - OEIS

%I #7 Dec 13 2015 16:32:02

%S 1620,14781,141759,1419921,14528199,150387285,1567749888,16417626507,

%T 172416155157,1814112395499,19110547682607,201479426103099,

%U 2125267836114957,22425737682248088,236688761385595083

%N Number of (n+1) X 4 0..2 arrays with the number of clockwise edge increases in 2 X 2 subblocks nondecreasing, and counterclockwise edge increases nonincreasing, rightwards and downwards.

%C Column 3 of A206542.

%H R. H. Hardin, <a href="/A206537/b206537.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = 26*a(n-1) -169*a(n-2) -962*a(n-3) +15074*a(n-4) -23548*a(n-5) -388835*a(n-6) +1661306*a(n-7) +3387121*a(n-8) -32428954*a(n-9) +18217134*a(n-10) +298256916*a(n-11) -598690104*a(n-12) -1238898284*a(n-13) +4947375888*a(n-14) +248363732*a(n-15) -19612727472*a(n-16) +17680860320*a(n-17) +37546981780*a(n-18) -68886915424*a(n-19) -19805672744*a(n-20) +117856544624*a(n-21) -46294103104*a(n-22) -94823075520*a(n-23) +86888550208*a(n-24) +22051127568*a(n-25) -55468199168*a(n-26) +13452820320*a(n-27) +12246999328*a(n-28) -7344098112*a(n-29) +380505984*a(n-30) +639121152*a(n-31) -167178240*a(n-32) +11612160*a(n-33) for n>37.

%e Some solutions for n=4:

%e ..2..1..1..1....0..1..0..0....2..1..0..2....0..0..2..2....2..2..0..0

%e ..1..1..2..1....0..0..0..2....1..2..1..0....0..2..2..0....2..0..0..2

%e ..1..2..2..2....0..1..0..0....2..1..0..1....2..2..0..0....2..0..2..2

%e ..1..2..0..2....0..0..0..1....0..2..1..0....2..0..0..1....0..0..2..1

%e ..1..2..2..2....1..0..2..2....1..0..2..1....2..2..2..1....2..2..2..1

%K nonn

%O 1,1

%A _R. H. Hardin_, Feb 09 2012