OFFSET
1,1
COMMENTS
Row 2 of A212232
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
a(n) = [x^(2*n)] (1+z+z^2)^(2*n-1)*(1+3*z+5*z^2)/(1-z). - Robert Israel, Mar 06 2018
EXAMPLE
Some solutions for n=3
..0....0....0....1....1....0....1....0....1....0....1....1....0....0....2....1
..0....0....0....1....0....2....1....2....0....2....1....0....0....1....1....1
..1....0....2....0....1....0....0....2....0....1....1....1....0....0....0....2
..2....1....1....2....1....0....2....0....0....0....2....2....2....0....1....0
..0....1....0....1....2....1....0....0....1....2....1....0....1....1....2....1
..2....1....1....0....1....1....1....0....2....0....0....0....0....1....0....0
..0....0....0....2....0....2....1....2....1....1....0....1....0....1....0....2
MAPLE
f:= proc(n) local S;
S:= series((1+z+z^2)^(2*n-1)*(1+3*z+5*z^2)/(1-z), z, 2*n+1);
coeff(S, z, 2*n);
end proc:
map(f, [$1..50]); # Robert Israel, Mar 06 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin May 06 2012
STATUS
approved