|
|
A180762
|
|
Half the number of nX2 binary arrays with each element equal to at least one neighbor
|
|
11
|
|
|
1, 3, 11, 34, 111, 361, 1172, 3809, 12377, 40218, 130687, 424661, 1379916, 4483973, 14570461, 47346034, 153848731, 499924281, 1624480652, 5278674169, 17152805697, 55737242698, 181115572487, 588526611821, 1912389796556, 6214221516093
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
COMMENTS
|
|
|
LINKS
|
|
|
FORMULA
|
Empirical: a(n) = 3*a(n-1) + a(n-2) - 2*a(n-4).
Empirical G.f.: x*(1-x)*(1+x+2*x^2)/(1-3*x-x^2+2*x^4). [Colin Barker, Feb 22 2012]
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|