|
|
A251285
|
|
Number of (n+1) X (1+1) 0..1 arrays with every 2 X 2 subblock having a single 1 or two 1s on the same edge or main diagonally.
|
|
1
|
|
|
9, 22, 52, 125, 297, 710, 1691, 4036, 9621, 22951, 54727, 130529, 311280, 742388, 1770476, 4222417, 10069902, 24015598, 57274225, 136592357, 325756272, 776890181, 1852790060, 4418684023, 10538033895, 25131955837, 59936717455
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
LINKS
|
|
|
FORMULA
|
Empirical: a(n) = 2*a(n-1) + 2*a(n-2) - 3*a(n-3) + a(n-4).
Empirical g.f.: x*(9 + 4*x - 10*x^2 + 4*x^3) / (1 - 2*x - 2*x^2 + 3*x^3 - x^4). - Colin Barker, Nov 28 2018
|
|
EXAMPLE
|
Some solutions for n=4:
..0..0....0..1....0..0....0..1....0..1....1..0....1..1....1..0....1..0....0..0
..1..1....0..0....0..1....0..0....0..0....0..0....0..0....1..0....1..0....0..1
..0..0....0..1....0..0....0..1....1..0....1..0....1..0....1..0....0..1....0..1
..0..1....0..0....1..0....0..1....0..0....0..0....0..1....0..0....0..0....0..0
..0..0....0..1....1..0....0..1....1..0....1..1....0..0....1..1....1..0....1..0
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|