login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A194488 Number of ways to arrange 4 nonattacking knights on the lower triangle of an n X n board 1
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

..0.0......1.1......1.0......1.1......0.0......0.0......0.0......1.0

..1.0.0....1.0.0....0.0.0....0.0.0....0.0.0....0.0.0....0.0.0....0.0.0

..0.1.0.1..0.0.0.0..0.0.1.1..0.0.0.1..1.1.0.1..1.0.1.1..0.1.1.1..1.0.1.1

CROSSREFS

Sequence in context: A131540 A218997 A279523 * A132932 A231787 A173716

Adjacent sequences:  A194485 A194486 A194487 * A194489 A194490 A194491

KEYWORD

nonn

AUTHOR

R. H. Hardin Aug 26 2011

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified June 12 08:13 EDT 2021. Contains 344943 sequences. (Running on oeis4.)