A036999 Restricted permutations. (Formerly N1692)

6, 9, 12, 18, 27, 42, 66, 105, 168, 270, 435, 702, 1134, 1833, 2964, 4794, 7755, 12546, 20298, 32841, 53136, 85974, 139107, 225078, 364182, 589257, 953436, 1542690, 2496123, 4038810, 6534930, 10573737, 17108664, 27682398, 44791059

Offset

0,1

References

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

Links

Vincenzo Librandi, Table of n, a(n) for n = 0..1000

N. S. Mendelsohn, Permutations with confined displacement, Canad. Math. Bull., 4 (1961), 29-38.

Index entries for linear recurrences with constant coefficients, signature (2, 0, -1).

Formula

3*A000381.

G.f.: 3*(2-x-2*x^2)/((x^2+x-1)*(x-1)). - Vincenzo Librandi, Jul 01 2017

Mathematica

Join[{6}, Table[3 Fibonacci[n+3] + 3, {n, 0, 40}]] (* or *) CoefficientList[Series[3 (2 - x - 2 x^2) / ((x^2 + x - 1) (x - 1)), {x, 0, 33}], x] (* Vincenzo Librandi, Jul 01 2017 *)

Prog

(Magma) [6] cat [3*Fibonacci(n+3)+3: n in [0..40]]; // Vincenzo Librandi, Jul 01 2017

Crossrefs

Equals A022086(n+3) + 3.

Sequence in context: A315958 A315959 A023386 * A290130 A118782 A246356

Adjacent sequences: A036996 A036997 A036998 * A037000 A037001 A037002

Keyword

nonn

Author

N. J. A. Sloane

Status

approved