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A264551 Number of (2+1) X (n+1) arrays of permutations of 0..n*3+2 with each element having directed index change -1,1 -1,2 1,0 or 0,-1.

%I A264551 #8 Jan 08 2019 19:00:44
%S A264551 1,2,6,16,40,96,240,608,1536,3840,9600,24064,60416,151552,379904,
%T A264551 952320,2387968,5988352,15015936,37650432,94404608,236716032,
%U A264551 593559552,1488322560,3731881984,9357492224,23463460864,58833502208,147522060288
%N A264551 Number of (2+1) X (n+1) arrays of permutations of 0..n*3+2 with each element having directed index change -1,1 -1,2 1,0 or 0,-1.
%H A264551 R. H. Hardin, <a href="/A264551/b264551.txt">Table of n, a(n) for n = 1..210</a>
%F A264551 Empirical: a(n) = 2*a(n-1) + 8*a(n-4).
%F A264551 Empirical g.f.: x*(1 + 2*x^2 + 4*x^3) / (1 - 2*x - 8*x^4). - _Colin Barker_, Jan 08 2019
%e A264551 Some solutions for n=4:
%e A264551 ..1..2..6..4..8....1..5..3..4..8....1..5..3..7..8....1..2..5..4..8
%e A264551 ..0.10.11..3.13....0.10..2.12.13....0.10..2.12..4....0..7.10..3.12
%e A264551 ..5.12..7.14..9...11..6..7.14..9...11..6.13.14..9...11..6.13.14..9
%Y A264551 Row 2 of A264550.
%K A264551 nonn
%O A264551 1,2
%A A264551 _R. H. Hardin_, Nov 17 2015