OFFSET
1,2
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 4*a(n-1) - 5*a(n-2) + 2*a(n-3) - 2*a(n-5) + 3*a(n-6) - a(n-8) for n>9.
Empirical g.f.: x*(1 + 2*x - 7*x^2 + 11*x^3 + 13*x^4 + 7*x^5 + 8*x^6 + 5*x^7 + 2*x^8) / ((1 - x)^2*(1 + x^2)*(1 - x - x^2)^2). - Colin Barker, Jan 02 2019
EXAMPLE
Some solutions for n=4:
..1..3..6..8..9....1..5..7..8..9....2..5..6..8..9....1..2..3..8..9
..7..0..5..2..4....6..0..2..3..4....7..0..1..3..4....6..0..5..4..7
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 22 2015
STATUS
approved