A212022 - OEIS

%I #5 Dec 18 2015 18:18:10

%S 0,2,25,346,2589,12636,46612,141520,372416,878329,1899446,3828397,

%T 7278790,13174461,22863219,38259181,62018107,97750460,150277231,

%U 225933884,332928091,481757242,685692030

%N 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, diagonal or antidiagonal neighbor, and containing the value n(n+1)/2-3

%C Column 2 of A212026

%F Empirical: a(n) = (1/128)*n^8 + (1/32)*n^7 - (41/192)*n^6 - (1/4)*n^5 + (345/128)*n^4 - (367/96)*n^3 - (47/96)*n^2 + (97/24)*n - 1 for n>1

%e Some solutions for n=4

%e ..0........0........0........0........0........0........0........0

%e ..0.1......1.2......1.2......0.1......1.2......1.2......0.1......1.2

%e ..2.1.3....3.4.5....3.4.5....2.3.4....3.4.5....1.3.4....2.3.4....3.4.5

%e ..4.5.6.7..6.7.2.0..0.6.1.7..5.1.6.7..0.6.7.1..5.6.7.5..5.0.6.7..6.2.7.4

%K nonn

%O 1,2

%A _R. H. Hardin_ Apr 26 2012