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A194487 revision #6

A194487

Number of ways to arrange 3 nonattacking knights on the lower triangle of an n X n board

0, 1, 12, 62, 253, 804, 2136, 4958, 10376, 20013, 36144, 61846, 101163, 159286, 242748, 359634, 519806, 735143, 1019796, 1390458, 1866649, 2471016, 3229648, 4172406, 5333268, 6750689, 8467976, 10533678, 13001991, 15933178, 19394004

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,3

COMMENTS

Column 3 of A194492

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..200

FORMULA

Empirical: a(n) = (1/48)*n^6 + (1/16)*n^5 - (17/16)*n^4 + (133/48)*n^3 + (433/24)*n^2 - (743/6)*n + 218 for n>4

EXAMPLE

Some solutions for 3X3

..1......0......1......1......0......0......1......0......0......0......1