OFFSET
0,3
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..1000
Andrei Asinowski, Cyril Banderier, and Valerie Roitner, Generating functions for lattice paths with several forbidden patterns, (2019).
Daniel Birmajer, Juan B. Gil, and Michael D. Weiner, On the Enumeration of Restricted Words over a Finite Alphabet, J. Int. Seq. 19 (2016) # 16.1.3, Example 10.
Richard J. Mathar, Paving rectangular regions with rectangular tiles: Tatami and Non-Tatami Tilings, arXiv:1311.6135 [math.CO], 2013, Table 1.
Richard J. Mathar, Bivariate Generating Functions Enumerating Non-Bonding Dominoes on Rectangular Boards, arXiv:2404.18806 [math.CO], 2024. See p. 7.
Index entries for linear recurrences with constant coefficients, signature (1,0,1).
FORMULA
For n >= 3, a(n) = a(n-1) + a(n-3).
a(n) = A000930(n+1).
From Frank Ruskey, Jun 07 2009: (Start)
G.f.: (1+x^2)/(1-x-x^3).
a(n) = Sum_{j=0..floor(n/2)} binomial(n-2j+1, j). (End)
G.f.: Q(0)*( 1+x^2 )/2, where Q(k) = 1 + 1/(1 - x*(4*k+1 + x^2)/( x*(4*k+3 + x^2) + 1/Q(k+1) )); (continued fraction). - Sergei N. Gladkovskii, Sep 08 2013
MATHEMATICA
LinearRecurrence[{1, 0, 1}, {1, 1, 2}, 42] (* Robert G. Wilson v, Jul 12 2014 *)
PROG
(PARI) my(x='x+O('x^50)); Vec((1+x^2)/(1-x-x^3)) \\ G. C. Greubel, Apr 26 2017
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Dean Hickerson, Mar 11 2002
STATUS
approved