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A305074 a(n) = 20*n - 8 (n>=1).

%I A305074 #16 May 29 2018 16:47:07
%S A305074 12,32,52,72,92,112,132,152,172,192,212,232,252,272,292,312,332,352,
%T A305074 372,392,412,432,452,472,492,512,532,552,572,592,612,632,652,672,692,
%U A305074 712,732,752,772,792,812,832,852,872,892,912,932,952,972,992
%N A305074 a(n) = 20*n - 8 (n>=1).
%C A305074 a(n) is the first Zagreb index of the single oxide chain SOX(n), defined pictorially in the Simonraj et al. reference (Fig. 4, where SOX(9) is shown,  marked as OX(1,9)).
%C A305074 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.
%C A305074 The M-polynomial of SL(n) is M(SL(n); x, y) = 2*x^2*y^2 + 2*n*x^2*y^4 + (n  - 2)*x^4*y^4 (n>=2).
%H A305074 Muniru A Asiru, <a href="/A305074/b305074.txt">Table of n, a(n) for n = 1..5000</a>
%H A305074 E. Deutsch and Sandi Klavzar, <a href="http://dx.doi.org/10.22052/ijmc.2015.10106">M-polynomial and degree-based topological indices</a>, Iranian J. Math. Chemistry, 6, No. 2, 2015, 93-102.
%H A305074 F. Simonraj and A. George, <a href="http://doi.org/10.7763/IJFCC.2013.V2.128">Topological properties of few poly oxide, poly silicate, DOX and DSL networks</a>, International J. of Future Computer and Communication, 2, No. 2, 2013, 90-95.
%H A305074 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1).
%F A305074 From _Colin Barker_, May 29 2018: (Start)
%F A305074 G.f.: 4*x*(3 + 2*x) / (1 - x)^2.
%F A305074 a(n) = 2*a(n-1) - a(n-2) for n>2.
%F A305074 (End)
%p A305074 seq(-8+20*n, n = 1 .. 50);
%o A305074 (GAP) List([1..50], n->20*n-8); # _Muniru A Asiru_, May 27 2018
%o A305074 (PARI) Vec(4*x*(3 + 2*x) / (1 - x)^2 + O(x^50)) \\ _Colin Barker_, May 29 2018
%Y A305074 Cf. A305075.
%K A305074 nonn,easy
%O A305074 1,1
%A A305074 _Emeric Deutsch_, May 26 2018