

A204678


Number of n X 1 0..3 arrays with no occurrence of three equal elements in a row horizontally, vertically, diagonally or antidiagonally, and new values 0..3 introduced in row major order.


5



1, 2, 4, 12, 40, 143, 528, 1979, 7466, 28246, 106992, 405481, 1537042, 5826959, 22091016, 83752328, 317527448, 1203835147, 4564081020, 17303737555, 65603438014, 248721498050, 942974761824, 3575088704597, 13554190277870
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OFFSET

1,2


COMMENTS

Column 1 of A204685.


LINKS

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


FORMULA

Empirical: a(n) = 4*a(n1) + a(n2)  6*a(n3)  3*a(n4) for n>6.
Empirical g.f.: x*(1 + x)*(1  3*x  2*x^2 + 2*x^3 + x^4) / ((1  x  x^2)*(1  3*x  3*x^2)).  Colin Barker, Feb 19 2018


EXAMPLE

Some solutions for n=5:
..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0
..1....1....1....0....1....0....0....1....0....1....0....0....0....1....1....0
..1....2....0....1....0....1....1....0....1....1....1....1....1....0....0....1
..0....1....2....0....0....0....0....1....0....0....0....1....0....0....0....0
..0....0....0....0....1....2....0....0....0....0....0....0....1....1....1....0


CROSSREFS

Sequence in context: A056236 A300652 A028329 * A025227 A211965 A119430
Adjacent sequences: A204675 A204676 A204677 * A204679 A204680 A204681


KEYWORD

nonn


AUTHOR

R. H. Hardin, Jan 18 2012


STATUS

approved



