A223882 Number of n X 2 0..2 arrays with row sums unimodal and column sums inverted unimodal.
9, 81, 564, 3298, 17048, 80412, 353485, 1469903, 5845411, 22414731, 83409546, 302722400, 1075880306, 3756503134, 12919764299, 43865509013, 147290172421, 489846413077, 1615582428816, 5289834522606, 17210293320924, 55679866275376
Offset: 1
Keywords
Examples
Some examples for n=3: ..0..1....0..0....1..1....0..1....0..0....1..2....0..0....0..1....0..2....2..2 ..0..2....1..2....2..2....2..0....1..0....2..2....0..0....0..2....2..2....0..2 ..2..0....2..2....0..0....1..1....1..2....0..2....0..0....1..1....1..1....0..1
Links
- R. H. Hardin, Table of n, a(n) for n = 1..210
Crossrefs
Cf. A223885.
Formula
Empirical: a(n) = 17*a(n-1) - 126*a(n-2) + 534*a(n-3) - 1425*a(n-4) + 2481*a(n-5) - 2816*a(n-6) + 2008*a(n-7) - 816*a(n-8) + 144*a(n-9).
Empirical g.f.: x*(9 - 72*x + 321*x^2 - 890*x^3 + 1617*x^4 - 1936*x^5 + 1480*x^6 - 672*x^7 + 144*x^8) / ((1 - x)^3*(1 - 2*x)^4*(1 - 3*x)^2). - Colin Barker, Aug 24 2018
Comments