A212040 Number of lower triangular n X n arrays colored with integers 0 upwards introduced in row major order, with no element equal to any element within a city block distance of two, and containing the value n(n+1)/2-3

0, 1, 5, 119, 1310, 7849, 32696, 107400, 298404, 731960, 1630174, 3361016, 6505445, 11945114, 20974435, 35441099, 57919461, 91921515, 142150499, 214802485, 317921624, 461815031

Offset

1,3

Comments

Column 2 of A212044

Links

Table of n, a(n) for n=1..22.

Formula

Empirical: a(n) = (1/128)*n^8 + (1/32)*n^7 - (77/192)*n^6 - (3/16)*n^5 + (977/128)*n^4 - (1885/96)*n^3 + (1129/96)*n^2 + (355/24)*n - 15 for n>1

Example

Some solutions for n=4
..0........0........0........0........0........0........0........0
..1.2......1.2......1.2......1.2......1.2......1.2......1.2......1.2
..3.4.5....3.0.4....3.4.5....3.4.5....3.4.5....3.4.1....3.4.1....3.4.5
..6.0.7.1..5.6.7.3..6.1.7.4..5.0.6.7..6.0.7.2..5.6.7.0..5.6.7.4..6.0.7.6

Crossrefs

Sequence in context: A208387 A144998 A257865 * A067359 A156962 A065818

Adjacent sequences: A212037 A212038 A212039 * A212041 A212042 A212043

Keyword

nonn

Author

R. H. Hardin Apr 28 2012

Status

approved