OFFSET
1,2
COMMENTS
Column 2 of A224333.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
Index entries for linear recurrences with constant coefficients, signature (8,-22,24,-9).
FORMULA
a(n) = n*(2*3^(n-1)-1).
a(n) = 8*a(n-1) - 22*a(n-2) + 24*a(n-3) - 9*a(n-4).
G.f.: x*(1 + 2*x - 7*x^2) / ((1 - x)^2*(1 - 3*x)^2). - Colin Barker, Aug 29 2018
EXAMPLE
Some solutions for n=3:
..1..0..0....1..0..0....1..0..0....1..1..0....1..0..0....1..0..1....1..0..0
..0..0..2....0..1..0....0..1..2....0..0..0....0..0..1....0..1..2....0..1..0
..0..0..1....0..0..0....0..0..0....0..2..1....0..0..1....0..0..0....1..0..0
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
R. H. Hardin, formula via M. F. Hasler William J. Keith and Rob Pratt in the Sequence Fans Mailing List, Apr 03 2013
STATUS
approved