OFFSET
1,1
COMMENTS
a(n) is the second Zagreb index of the hex derived network HDN1(n) from the Manuel et al. reference (see HDN1(4) in Fig. 8).
The second Zagreb index of a simple connected graph is the sum of the degree products d(i)d(j) over all edges ij of the graph.
The M-polynomial of HDN1(n) is M(HDN1(n);x,y) = 12*x^3*y^5 + (18*(n-2))*x^3*y^7 + (6*(3*n^2-9*n+7))*x^3*y^12 + 12*x^5*y^7 + 6*x^5*y^12 + (6*(n-3))*x^7*y^7 + (12*(n-2))*x^7*y^12 + (3*(n-2)*(3*n-5)*x^12*y^12.
LINKS
Colin Barker, Table of n, a(n) for n = 1..1000
E. Deutsch and Sandi Klavzar, M-polynomial and degree-based topological indices, Iranian J. Math. Chemistry, 6, No. 2, 2015, 93-102.
P. Manuel, R. Bharati, I. Rajasingh, and Chris Monica M, On minimum metric dimension of honeycomb networks, J. Discrete Algorithms, 6, 2008, 20-27.
Index entries for linear recurrences with constant coefficients, signature (3,-3,1).
FORMULA
G.f.: 6*x*(11 + 114*x + 523*x^2)/(1 - x)^3. - Bruno Berselli, May 22 2018
MAPLE
seq(3138 - 5016*n + 1944*n^2, n = 1 .. 45);
MATHEMATICA
Table[1944 n^2 - 5016 n + 3138, {n, 1, 40}] (* Bruno Berselli, May 22 2018 *)
LinearRecurrence[{3, -3, 1}, {66, 882, 5586}, 40] (* Harvey P. Dale, Dec 02 2018 *)
PROG
(GAP) List([1..50], n->1944*n^2-5016*n+3138); # Muniru A Asiru, May 22 2018
(PARI) Vec(6*x*(11 + 114*x + 523*x^2)/(1 - x)^3 + O(x^40)) \\ Colin Barker, May 23 2018
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Emeric Deutsch, May 21 2018
STATUS
approved