|
%I #9 Jan 04 2019 09:02:15
%S 9,39,169,715,3025,12815,54289,229971,974169,4126647,17480761,
%T 74049691,313679521,1328767775,5628750625,23843770275,101003831721,
%U 427859097159,1812440220361,7677619978603,32522920134769,137769300517679
%N Number of (n+1) X (2+1) arrays of permutations of 0..n*3+2 with each element having index change +-(.,.) 0,0 0,1 or 2,-2.
%H R. H. Hardin, <a href="/A264085/b264085.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = 4*a(n-1) + 4*a(n-3) + a(n-4).
%F Empirical g.f.: x*(9 + 3*x + 13*x^2 + 3*x^3) / ((1 + x^2)*(1 - 4*x - x^2)). - _Colin Barker_, Jan 04 2019
%e Some solutions for n=4:
%e ..1..0..2....0..1..6....0..2..1....1..0..2....0..2..1....1..0..6....1..0..6
%e ..3..4..5....3..5..4....4..3..5....3..5..4....4..3..5....3..4..5....4..3..5
%e ..7..6..8....2..8..7....6..8..7....7..6.12....6..7.12....2..7..8....2..8..7
%e ..9.10.11....9.10.11....9.10.11....9.10.11....9.10.11....9.10.11....9.11.10
%e .12.14.13...12.14.13...12.14.13....8.14.13....8.14.13...12.14.13...12.13.14
%Y Column 2 of A264090.
%K nonn
%O 1,1
%A _R. H. Hardin_, Nov 03 2015
| 