Mohammad Reza Farahani, On the SD-Polynomial and SD-Index of an Infinite Class of “Armchair Polyhex Nanotubes”, Volume 31, International Letters of Chemistry, Physics and Astronomy (Volume 31) https://www.scipress.com/ILCPA.31.63 Abstract: Let G be a simple connected graph with the vertex set V = V(G) and the edge set E = E(G),without loops and multiple edges. For counting qoc strips in G, Diudea introduced the Ω-polynomialof G and was defined as Ω(G, x) = ∑<sup>k</sup><sub></sub><sub>i-1</sub>x<sub>i</sub> where C1, C2,..., Ck be the “opposite edge strips” ops of Gand ci = |Ci| (I = 1, 2,..., k). One can obtain the Sd-polynomial by replacing xc with x<sup>|E(G)|-c</sup> in Ω-polynomial. Then the Sd-index will be the first derivative of Sd(x) evaluated at x = 1. In this paper wecompute the Sd-polynomial and Sd-index of an infinite class of “Armchair Polyhe x Nanotubes”. Keywords: Armchair Polyhex Nanotubes Andnanotori, Omega and Sadhana Polynomial, Sadhana Index