OFFSET
1,1
COMMENTS
Row 3 of A224333.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
Index entries for linear recurrences with constant coefficients, signature (3,-3,1).
FORMULA
a(n) = 6*n^2 + 12*n + 3.
From Colin Barker, Feb 23 2018: (Start)
G.f.: 3*x*(7 - 4*x + x^2) / (1 - x)^3.
a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n>3.
(End)
EXAMPLE
Some solutions for n=3:
..1..2..0....1..0..0....1..0..0....1..0..1....1..0..2....0..0..0....0..0..0
..0..0..0....1..0..2....0..1..0....0..1..3....0..1..2....3..1..0....1..1..0
..0..1..1....0..0..1....0..0..0....0..0..0....0..0..0....1..0..1....2..0..1
PROG
(PARI) a(n) = 6*n^2 + 12*n + 3 \\ Charles R Greathouse IV, Jun 17 2017
(PARI) Vec(3*x*(7 - 4*x + x^2) / (1 - x)^3 + O(x^60)) \\ Colin Barker, Feb 23 2018
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