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A304171 a(n) = 87*2^n - 38 (n>=0). 2
49, 136, 310, 658, 1354, 2746, 5530, 11098, 22234, 44506, 89050, 178138, 356314, 712666, 1425370, 2850778, 5701594, 11403226, 22806490, 45613018, 91226074, 182452186, 364904410, 729808858, 1459617754, 2919235546, 5838471130, 11676942298, 23353884634, 46707769306 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

a(n) is the number of vertices in the N-branched phenylacetylene NSB[n], shown pictorially in the Yarahmadi reference (for n=2).

LINKS

Colin Barker, Table of n, a(n) for n = 0..1000

Z. Yarahmadi and G. H. Fath-Tabar, The Wiener, Szeged, PI, Vertex PI, the first and second Zagreb indices of N-branched phenylacetylenes dendrimers, MATCH: Commun. Math. Comput. Chem, 65 (2011) 201-208.

Index entries for linear recurrences with constant coefficients, signature (3,-2).

FORMULA

From Colin Barker, May 10 2018: (Start)

G.f.: (49 - 11*x) / ((1 - x)*(1 - 2*x)).

a(n) = 3*a(n-1) - 2*a(n-2) for n>1.

(End)

MAPLE

seq(87*2^n-38, n = 0 .. 35);

PROG

(PARI) Vec((49 - 11*x) / ((1 - x)*(1 - 2*x)) + O(x^30)) \\ Colin Barker, May 10 2018

(GAP) List([0..40], n->87*2^n-38); # Muniru A Asiru, May 10 2018

CROSSREFS

Cf. A304172.

Sequence in context: A304674 A257524 A020256 * A118160 A211501 A009404

Adjacent sequences:  A304168 A304169 A304170 * A304172 A304173 A304174

KEYWORD

nonn,easy

AUTHOR

Emeric Deutsch, May 10 2018

STATUS

approved

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Last modified May 30 18:38 EDT 2020. Contains 334728 sequences. (Running on oeis4.)