A278621 Number of nX2 0..2 arrays with rows in nondecreasing lexicographic order and columns in nonincreasing lexicographic order, but with exactly one mistake.

3, 46, 357, 1952, 8518, 31605, 103546, 307087, 838936, 2138608, 5137407, 11719956, 25549096, 53493458, 108027996, 211167710, 400765157, 740380790, 1334456849, 2351234708, 4056807390, 6864961455, 11409118950, 18644841765, 29994129570

Offset: 1

Author

R. H. Hardin, Nov 24 2016

Keywords

• nonn

Comments

Column 2 of A278627.

Examples

			Some solutions for n=4
..2..0. .0..0. .1..0. .0..1. .2..0. .0..0. .1..0. .2..2. .2..2. .0..0
..0..0. .2..2. .1..2. .1..2. .2..0. .1..0. .1..2. .1..1. .2..2. .2..1
..2..1. .1..1. .2..2. .2..0. .2..1. .2..2. .2..1. .2..1. .2..2. .0..2
..2..1. .2..0. .0..0. .2..0. .1..2. .0..0. .0..1. .2..2. .0..0. .1..0
		

Links

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

Crossrefs

Cf. A278627.

Formula

Empirical: a(n) = (1/1307674368000)*n^15 + (1/12454041600)*n^14 + (149/37362124800)*n^13 + (17/136857600)*n^12 + (3497/1306368000)*n^11 + (241/5806080)*n^10 + (865163/1828915200)*n^9 + (351247/87091200)*n^8 + (2328827/93312000)*n^7 + (698341/6220800)*n^6 + (259070737/718502400)*n^5 + (30620411/39916800)*n^4 + (8765485871/9081072000)*n^3 + (2221837/3603600)*n^2 + (4873/32760)*n