login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A208402 Number of n X 2 0..3 arrays with new values 0..3 introduced in row major order and no element equal to more than two of its immediate leftward or upward or right-upward antidiagonal neighbors. 1

%I

%S 2,15,187,2795,43947,700075,11188907,178973355,2863377067,45813246635,

%T 733008800427,11728128223915,187650001250987,3002399818689195,

%U 48038396293720747,768614337478306475,12297829386768001707

%N Number of n X 2 0..3 arrays with new values 0..3 introduced in row major order and no element equal to more than two of its immediate leftward or upward or right-upward antidiagonal neighbors.

%C Column 2 of A208408.

%H R. H. Hardin, <a href="/A208402/b208402.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = 21*a(n-1) - 84*a(n-2) + 64*a(n-3).

%F Conjectures from _Colin Barker_, Jul 02 2018: (Start)

%F G.f.: x*(2 - 27*x + 40*x^2) / ((1 - x)*(1 - 4*x)*(1 - 16*x)).

%F a(n) = (8 + 3*2^(1+2*n) + 16^n) / 24.

%F (End)

%e Some solutions for n=4:

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

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

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

%e ..2..0....1..0....2..0....1..0....3..2....1..1....0..2....2..2....0..1....1..2

%Y Cf. A208408.

%K nonn

%O 1,1

%A _R. H. Hardin_, Feb 26 2012

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified September 26 14:21 EDT 2022. Contains 356999 sequences. (Running on oeis4.)