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A194489
Number of ways to arrange 5 nonattacking knights on the lower triangle of an n X n board
1
0, 0, 0, 13, 387, 3727, 23496, 111433, 429343, 1407755, 4061432, 10561723, 25208796, 55996244, 117021864, 232070481, 439779278, 800893832, 1408234986, 2400123737, 3978154435, 6430366713, 10161044648, 15728568633, 23892962265, 35675014169
OFFSET
1,4
COMMENTS
Column 5 of A194492
LINKS
FORMULA
Empirical: a(n) = (1/3840)*n^10 + (1/768)*n^9 - (17/384)*n^8 + (3/128)*n^7 + (951/256)*n^6 - (68939/3840)*n^5 - (1433/12)*n^4 + (230047/192)*n^3 - (149581/240)*n^2 - (718267/30)*n + 72425 for n>10
EXAMPLE
Some solutions for 4X4
..1........1........0........0........1........1........1........1
..0.0......0.1......0.1......0.1......1.1......1.0......0.0......0.0
..1.0.1....1.0.1....1.0.1....1.1.1....1.0.0....0.0.0....0.0.0....0.0.1
..0.1.0.1..0.1.0.0..0.1.0.1..0.1.0.0..0.0.0.1..1.0.1.1..1.1.1.1..0.1.1.1
CROSSREFS
Sequence in context: A142122 A370379 A302700 * A354138 A356740 A275651
KEYWORD
nonn
AUTHOR
R. H. Hardin Aug 26 2011
STATUS
approved