A189594 Number of permutations of 1..n with displacements restricted to {-6,-5,-4,-3,-1,0,2}.

1, 1, 2, 4, 10, 23, 51, 111, 225, 469, 997, 2125, 4569, 9742, 20728, 44075, 93629, 199251, 424146, 902940, 1922351, 4091125, 8706560, 18528914, 39433024, 83926690, 178622780, 380165386, 809106324, 1722001443, 3664905891, 7799962633

Offset: 1

Author

R. H. Hardin Apr 24 2011

Keywords

• nonn

Examples

			Some solutions for n=11
..1....4....1....1....1....1....1....2....4....1....6....1....1....5....5....4
..2....7....2....6....7....5....7....8....3....5....5....2....5....3....2....3
..3....1....3....3....6....4....3....1....1....6....1....7....3....1....1....1
..5....2....7....2....2....2....2....5....2....2....2....4....2....2....4....2
..6....3....5....5....3....3....9....3....6....3....3....3....6....6....3....6
..4...10....4....4....4...11....4....4....7....4....4....6....4....4....6...10
.10....5...10....7....5....8....5...10....5....7....8....5....8....7....8....5
.11....6....6...11...11....6....6....6...11....8....9...11...11....8....9....8
..7....9....9...10...10....7...10....7...10...10....7...10....7....9....7....7
..8....8....8....8....8...10....8...11....8...11...10....8...10...10...10...11
..9...11...11....9....9....9...11....9....9....9...11....9....9...11...11....9
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..200

Formula

Empirical: a(n) = a(n-1) +2*a(n-3) +2*a(n-4) +5*a(n-5) +4*a(n-6) +9*a(n-7) +13*a(n-8) -5*a(n-9) +6*a(n-10) -17*a(n-11) -14*a(n-12) -2*a(n-13) -11*a(n-14) -2*a(n-15) -11*a(n-16) -4*a(n-17) -2*a(n-18) +5*a(n-19) +7*a(n-20) +2*a(n-21) +2*a(n-22) +2*a(n-23) +a(n-24) +a(n-25) +a(n-26) -a(n-27) -a(n-28)