cp's OEIS Frontend

A206500 Number of nX3 0..7 arrays with no element equal to another within a city block distance of two, and new values 0..7 introduced in row major order.

%I A206500 #8 Jul 22 2025 19:29:05
%S A206500 1,4,65,3130,178998,10502458,618242826,36410671102,2144479610070,
%T A206500 126304554589462,7439032094765766,438141046109721622,
%U A206500 25805450786659366998,1519878816318690262678,89517196729004371783830
%N A206500 Number of nX3 0..7 arrays with no element equal to another within a city block distance of two, and new values 0..7 introduced in row major order.
%C A206500 Column 3 of A206503
%H A206500 R. H. Hardin, <a href="/A206500/b206500.txt">Table of n, a(n) for n = 1..62</a>
%F A206500 Empirical: a(n) = 55*a(n-1) +370*a(n-2) -8556*a(n-3) +15608*a(n-4) +70028*a(n-5) -175808*a(n-6) +98304*a(n-7) for n>9
%e A206500 Some solutions for n=4
%e A206500 ..0..1..2....0..1..2....0..1..2....0..1..2....0..1..2....0..1..2....0..1..2
%e A206500 ..2..3..0....2..3..0....2..3..0....3..4..0....2..3..4....2..3..4....2..3..4
%e A206500 ..1..4..5....4..5..1....1..4..5....2..5..1....1..0..5....1..5..6....4..5..1
%e A206500 ..5..0..1....1..0..4....5..2..1....0..3..6....3..4..2....3..4..7....6..2..3
%K A206500 nonn
%O A206500 1,2
%A A206500 _R. H. Hardin_ Feb 08 2012