A211906 Number of lower triangular n X n arrays colored with integers 0 upwards introduced in row major order, with no element equal to any horizontal or vertical neighbor, and containing the value n(n+1)/2-3.
0, 2, 30, 418, 3006, 14201, 51157, 152650, 396538, 926011, 1987151, 3980637, 7530745, 13575108, 23479016, 39178351, 63355567, 99653440, 152931628, 229571396, 337834176, 488279947, 694251735
Offset: 1
Keywords
Examples
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....3.4.5....3.4.5....3.4.2....3.4.5....3.4.5....2.3.4....3.4.5 ..6.7.0.8..6.0.1.7..6.3.7.8..5.6.7.3..1.5.6.7..6.2.7.5..5.6.0.7..6.2.6.7
Formula
Empirical: a(n) = (1/128)*n^8 + (1/32)*n^7 - (29/192)*n^6 - (5/16)*n^5 + (193/128)*n^4 - (25/96)*n^3 - (275/96)*n^2 + (49/24)*n + 1 for n>1
Comments