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A198656 Number of nX2 0..7 arrays with values 0..7 introduced in row major order and each element equal to at least one horizontal or vertical neighbor.

%I A198656 #7 Jul 22 2025 13:03:13
%S A198656 1,3,14,76,488,3521,28030,242883,2267306,22621072,239604079,
%T A198656 2677734762,31381450817,383270472363,4847901589642,63125725801101,
%U A198656 841517900517550,11429291342102135,157506922063918536,2195111769933116471
%N A198656 Number of nX2 0..7 arrays with values 0..7 introduced in row major order and each element equal to at least one horizontal or vertical neighbor.
%C A198656 Column 2 of A198661
%H A198656 R. H. Hardin, <a href="/A198656/b198656.txt">Table of n, a(n) for n = 1..200</a>
%F A198656 Empirical: a(n) = 50*a(n-1) -973*a(n-2) +8874*a(n-3) -29927*a(n-4) -92230*a(n-5) +939984*a(n-6) -1157338*a(n-7) -7025352*a(n-8) +14473974*a(n-9) +29278108*a(n-10) -54017762*a(n-11) -108264239*a(n-12) +78120984*a(n-13) +276328733*a(n-14) +56831952*a(n-15) -336850101*a(n-16) -307076936*a(n-17) +88644128*a(n-18) +275952224*a(n-19) +124163560*a(n-20) -45062112*a(n-21) -62248400*a(n-22) -20707200*a(n-23) -2210000*a(n-24)
%e A198656 Some solutions with all values 0 to 7 for n=8
%e A198656 ..0..0....0..0....0..1....0..0....0..0....0..1....0..1....0..1....0..0....0..0
%e A198656 ..1..1....1..2....0..1....1..1....1..1....0..1....0..1....0..1....1..1....1..2
%e A198656 ..2..2....1..2....2..3....2..2....2..2....2..2....2..2....2..2....2..2....1..2
%e A198656 ..3..3....3..4....2..3....3..3....3..3....3..3....3..4....3..3....3..4....3..3
%e A198656 ..4..5....3..4....4..5....4..4....4..4....4..5....3..4....4..4....3..4....4..4
%e A198656 ..4..5....5..6....4..5....5..6....5..5....4..5....5..5....5..5....5..6....5..6
%e A198656 ..6..7....5..6....6..7....5..6....6..6....6..7....6..7....6..6....5..6....5..6
%e A198656 ..6..7....7..7....6..7....7..7....7..7....6..7....6..7....7..7....7..7....7..7
%K A198656 nonn
%O A198656 1,2
%A A198656 _R. H. Hardin_ Oct 28 2011