cp's OEIS Frontend

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.

%I A212040 #6 Jun 02 2025 07:54:35
%S A212040 0,1,5,119,1310,7849,32696,107400,298404,731960,1630174,3361016,
%T A212040 6505445,11945114,20974435,35441099,57919461,91921515,142150499,
%U A212040 214802485,317921624,461815031
%N 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.
%C A212040 Column 2 of A212044
%F A212040 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
%e A212040 Some solutions for n=4
%e A212040 ..0........0........0........0........0........0........0........0
%e A212040 ..1.2......1.2......1.2......1.2......1.2......1.2......1.2......1.2
%e A212040 ..3.4.5....3.0.4....3.4.5....3.4.5....3.4.5....3.4.1....3.4.1....3.4.5
%e A212040 ..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
%K A212040 nonn
%O A212040 1,3
%A A212040 _R. H. Hardin_ Apr 28 2012