OFFSET
1,3
COMMENTS
a(n) is an upper bound for the irregularity of a graph with n vertices (see Theorem 3.2 of the Tavakoli et al. reference).
LINKS
M. Tavakoli, F. Rahbarnia, M. Mirzavaziri, A. R. Ashrafi, and I. Gutman, Extremely irregular graphs, Kragujevac J. Math., 37 (1), 2013, 135-139.
Index entries for linear recurrences with constant coefficients, signature (2,-1,2,-4,2,-1,2,-1).
FORMULA
a(n) = 2*A200067(n).
G.f.: 2*x^3*(1+x)*(1+x^2) / ( (1+x+x^2)^2*(x-1)^4 ). - R. J. Mathar, Jul 22 2022
EXAMPLE
a(4) = floor(4/3)*(4 - floor(4/3))*(4-floor(4/3)-1) = 1*3*2 = 6.
MAPLE
a:=n->floor(n/3)*(n-floor(n/3))*(n-floor(n/3)-1): seq(a(n), n=1..50);
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Emeric Deutsch, Apr 14 2019
STATUS
approved