OFFSET
1,2
COMMENTS
Note that the index in Eq. (5) of the paper must be 2k-1, not 2k as published, to reproduce the numbers. - R. J. Mathar, Nov 23 2014
LINKS
Colin Barker, Table of n, a(n) for n = 1..1000
J. Brunvoll, S. J. Cyvin and B. N. Cyvin, Azulenoids, MATCH, No. 34, 1996, 91-108.
Index entries for linear recurrences with constant coefficients, signature (4,-4,1).
FORMULA
a(n) = 5*Fibonacci(2*k-1)-4 = A106729(k-1)-4.
G.f.: -x*(1+x)^2 / ( (x-1)*(x^2-3*x+1) ). - R. J. Mathar, Nov 23 2014
From Colin Barker, Nov 03 2016: (Start)
a(n) = 2^(-1-n)*(-2^(3+n)-(-5+sqrt(5))*(3+sqrt(5))^n+(3-sqrt(5))^n*(5+sqrt(5))).
a(n) = 4*a(n-1)-4*a(n-2)+a(n-3) for n>3. (End)
PROG
(PARI) Vec(-x*(1+x)^2/((x-1)*(x^2-3*x+1)) + O(x^40)) \\ Colin Barker, Nov 03 2016
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Sep 23 2006
STATUS
approved