A223571 Number of nX3 0..2 arrays with antidiagonals unimodal

27, 729, 16038, 352836, 7762392, 170772624, 3756997728, 82653950016, 1818386900352, 40004511807744, 880099259770368, 19362183714948096, 425968041728858112, 9371296918034878464, 206168532196767326208

Offset

1,1

Comments

Column 3 of A223576

Links

R. H. Hardin, Table of n, a(n) for n = 1..210

Formula

Let U(z) = (z^4+6*z^3+23*z^2+18*z+24)/24

a(n) = U(min(n,3))^(max(n,3)-min(n,3)+1) * product{ U(i)^2 , i=1..(min(n,3)-1) }

a(n) = 22*a(n-1) for n>2

Example

Some solutions for n=3
..1..2..1....1..2..2....0..1..0....0..1..0....0..2..0....2..0..0....2..1..0
..2..1..1....0..2..2....0..1..2....1..1..2....1..0..2....1..1..1....2..0..2
..2..0..0....2..1..0....1..2..1....2..2..1....1..0..0....1..1..0....1..2..2

Crossrefs

Sequence in context: A223976 A167726 A268022 * A228973 A171301 A098838

Adjacent sequences: A223568 A223569 A223570 * A223572 A223573 A223574

Keyword

nonn

Author

R. H. Hardin Mar 22 2013

Status

approved