cp's OEIS Frontend

A211905 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)/2-2.

%I A211905 #9 May 22 2014 03:34:45
%S A211905 0,2,10,34,86,181,337,575,919,1396,2036,2872,3940,5279,6931,8941,
%T A211905 11357,14230,17614,21566,26146,31417,37445,44299,52051,60776,70552,
%U A211905 81460,93584,107011,121831,138137,156025,175594,196946,220186,245422,272765,302329
%N A211905 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)/2-2.
%C A211905 Column 1 of A211910.
%H A211905 R. H. Hardin, <a href="/A211905/b211905.txt">Table of n, a(n) for n = 1..76</a>
%F A211905 Empirical: a(n) = (1/8)*n^4 + (1/4)*n^3 - (9/8)*n^2 + (3/4)*n + 1 for n>1.
%e A211905 Some solutions for n=4:
%e A211905 ..0........0........0........0........0........0........0........0
%e A211905 ..1.2......1.2......1.2......1.2......1.2......1.2......1.2......1.2
%e A211905 ..3.4.5....3.4.5....3.0.4....3.4.5....3.4.5....3.4.3....3.4.5....3.4.5
%e A211905 ..6.0.7.8..6.7.8.7..5.6.7.8..6.7.4.8..6.7.8.4..5.6.7.8..6.1.7.8..6.7.0.8
%K A211905 nonn
%O A211905 1,2
%A A211905 _R. H. Hardin_, Apr 25 2012