A194488 - OEIS

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A194488

Number of ways to arrange 4 nonattacking knights on the lower triangle of an n X n board

0, 0, 4, 46, 407, 2168, 8685, 28376, 79611, 198334, 449336, 942072, 1852096, 3449261, 6133944, 10482661, 17304542, 27710241, 43194961, 65737379, 97916361, 143047462, 205341311, 290086086, 403856389, 554750936, 752661582, 1009576306, 1339918886

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

OFFSET

1,3

COMMENTS

Column 4 of A194492

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..117

FORMULA

Empirical: a(n) = (1/384)*n^8 + (1/96)*n^7 - (17/64)*n^6 + (5/12)*n^5 + (1571/128)*n^4 - (6653/96)*n^3 - (8641/96)*n^2 + (13951/8)*n - 4161 for n>7

EXAMPLE

Some solutions for 4X4

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