

A305072


a(n) = 144*n^2  24*n (n>=1).


2



120, 528, 1224, 2208, 3480, 5040, 6888, 9024, 11448, 14160, 17160, 20448, 24024, 27888, 32040, 36480, 41208, 46224, 51528, 57120, 63000, 69168, 75624, 82368, 89400, 96720, 104328, 112224, 120408, 128880, 137640, 146688, 156024, 165648, 175560, 185760, 196248, 207024, 218088, 229440, 241080, 253008, 265224
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OFFSET

1,1


COMMENTS

a(n) is the first Zagreb index of the oxide network OX(n), defined pictorially in the Javaid et al. reference (Fig. 3, where OX(2) is shown) or in the Liu et al. reference (Fig. 6, where OX(5) is shown).
The first Zagreb index of a simple connected graph is the sum of the squared degrees of its vertices. Alternatively, it is the sum of the degree sums d(i) + d(j) over all edges ij of the graph.
The Mpolynomial of OX(n) is M(OX(n); x, y) = 12*n*x^2*y^4 + 6*n*(3*n  2)*x^4*y^4 (n>=1).


LINKS



FORMULA

G.f.: 24*x*(5 + 7*x) / (1  x)^3.
a(n) = 3*a(n1)  3*a(n2) + a(n3) for n>3.
(End)


MAPLE

seq(144*n^2  24*n, n = 1 .. 50);


PROG

(PARI) Vec(24*x*(5 + 7*x) / (1  x)^3 + O(x^50)) \\ Colin Barker, May 26 2018


CROSSREFS



KEYWORD

nonn,easy


AUTHOR



STATUS

approved



