A278628 Number of nX2 0..2 arrays with rows in nondecreasing lexicographic order and columns in nonincreasing lexicographic order, but with exactly two mistakes.

0, 13, 285, 3354, 27521, 175881, 932205, 4266912, 17344954, 63898594, 216606040, 683599110, 2027209742, 5691010421, 15216367989, 38944866772, 95817126997, 227430633270, 522402290790, 1164311022921, 2523775686270, 5331359865045

Offset

1,2

Comments

Column 2 of A278634.

Links

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

Formula

Empirical: a(n) = (1/620448401733239439360000)*n^24 + (1/2248001455555215360000)*n^23 + (61/1037539133333176320000)*n^22 + (23/4644631106519040000)*n^21 + (104341/350337889177436160000)*n^20 + (6949/512189896458240000)*n^19 + (710713/1466725612584960000)*n^18 + (37298267/2688996956405760000)*n^17 + (2447539049/7592461994557440000)*n^16 + (3869390387/632705166213120000)*n^15 + (564645080393/5965505852866560000)*n^14 + (32796029107/27618082652160000)*n^13 + (996499793624389/83517081940131840000)*n^12 + (59819000678947/632705166213120000)*n^11 + (84816399097571/146008884510720000)*n^10 + (428014613650991/158176291553280000)*n^9 + (1006691142411629/104766115184640000)*n^8 + (827938404705089/32011868528640000)*n^7 + (70267771340481037/1419192838103040000)*n^6 + (7292384715686149/118266069841920000)*n^5 + (279991448485477/7227370934784000)*n^4 - (11564797442491/361368546739200)*n^3 - (14612582504501/148419224553600)*n^2 - (71459/1225224)*n

Example

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

Crossrefs

Cf. A278634.

Sequence in context: A256044 A160294 A092145 * A035017 A064750 A228753

Adjacent sequences: A278625 A278626 A278627 * A278629 A278630 A278631

Keyword

nonn

Author

R. H. Hardin, Nov 24 2016

Status

approved