OFFSET
0,2
LINKS
M. A. Fiol, J. L. A. Yebra, I. Alegre, and M. Valero Discrete optimization problem in local networks and data alignment, IEEE Trans. Comput., C-36 (1987), no. 6, 702-713.
Index entries for linear recurrences with constant coefficients, signature (2,-1,1,-2,1).
FORMULA
a(n) = ceiling((n+2)^2/3)-1 for n<>1.
G.f.: (1 + x - x^4 + 2*x^5 - x^6)/((1 - x)^3*(1 + x + x^2)). - Stefano Spezia, Mar 13 2024
EXAMPLE
For n=10, the maximum number of vertices a(n)=47 is obtained, for instance, with the Cayley digraph Cay(47;1,11).
MATHEMATICA
CoefficientList[Series[(1 + x - x^4 + 2*x^5 - x^6)/((1 - x)^3*(1 + x + x^2)), {x, 0, 40}], x] (* or *) Join[{1, 3}, Table[Ceiling[(n+2)^2/3]-1, {n, 2, 40}]] (* James C. McMahon, Apr 04 2024 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Miquel A. Fiol, Mar 13 2024
STATUS
approved