cp's OEIS Frontend

A189581 Number of permutations of 1..n with displacements restricted to {-4,-3,0,1,2}.

%I A189581 #11 May 02 2018 15:22:52
%S A189581 1,1,1,4,13,26,48,95,205,456,974,2024,4225,8930,18977,40199,84815,
%T A189581 178867,377753,798542,1687806,3565554,7531030,15908857,33611337,
%U A189581 71013181,150026395,316943191,669573901,1414567938,2988489622,6313604894
%N A189581 Number of permutations of 1..n with displacements restricted to {-4,-3,0,1,2}.
%H A189581 R. H. Hardin, <a href="/A189581/b189581.txt">Table of n, a(n) for n = 1..200</a>
%F A189581 Empirical: a(n) = a(n-1) +2*a(n-3) +3*a(n-4) +5*a(n-5) +5*a(n-6) -a(n-8) -6*a(n-9) -a(n-10) -3*a(n-11) -a(n-12) +a(n-13) +a(n-15).
%F A189581 Empirical g.f.: x*(1 + x^3 + 4*x^4 + 3*x^5 + x^6 - x^7 - 5*x^8 - x^9 - 3*x^10 - x^11 + x^12 + x^14) / (1 - x - 2*x^3 - 3*x^4 - 5*x^5 - 5*x^6 + x^8 + 6*x^9 + x^10 + 3*x^11 + x^12 - x^13 - x^15). - _Colin Barker_, May 02 2018
%e A189581 Some solutions for n=11:
%e A189581 ..1....4....1....1....4....5....1....4....5....5....1....5....4....1....5....1
%e A189581 ..2....2....2....2....2....1....6....1....1....1....6....2....1....2....1....5
%e A189581 ..6....1....6....7....1....2....2....3....3....3....2....1....7....7....2....6
%e A189581 ..4....7....7....3....8....3....4....2....2....2....4....7....2....3....7....2
%e A189581 ..3....3....3....4....3....8....3....5....4....4....3....3....3....4....3....3
%e A189581 ..5....5....4....5....5....4...10....6....6...10....5....4....6....5....4....4
%e A189581 .10....6....5....6....6....6....5....7...10....6...10....6....5....6....6....7
%e A189581 ..7....8...11...11....7...11....7...11....8....7....8...11...11...11...11...11
%e A189581 ..9....9....9....8....9....7....8....9....7....8....7....8....9....8....9....8
%e A189581 ..8...10....8...10...10...10....9....8....9....9....9...10....8....9....8...10
%e A189581 .11...11...10....9...11....9...11...10...11...11...11....9...10...10...10....9
%K A189581 nonn
%O A189581 1,4
%A A189581 _R. H. Hardin_, Apr 24 2011