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A304615 a(n) = 507*2^n - 273. 4
234, 741, 1755, 3783, 7839, 15951, 32175, 64623, 129519, 259311, 518895, 1038063, 2076399, 4153071, 8306415, 16613103, 33226479, 66453231, 132906735, 265813743, 531627759, 1063255791, 2126511855, 4253023983, 8506048239, 17012096751, 34024193775, 68048387823, 136096775919, 272193552111 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,1
COMMENTS
a(n) is the second Zagreb index of the nanostar dendrimer NS[n] from the Mirzargar reference.
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 NS[n] is M(NS[n]; x,y) = (30*2^n - 12)*x^2*y^2 + (42*2^n - 24)*x^2*y^3 + (15*2^n - 9)*x^3*y^3.
LINKS
E. Deutsch and Sandi Klavzar, M-polynomial and degree-based topological indices, Iranian J. Math. Chemistry, 6, No. 2, 2015, 93-102.
M. Mirzargar, PI, Szeged and edge Szeged polynomials of a dendrimer nanostar, MATCH, Commun. Math. Comput. Chem. 62, 2009, 363-370.
FORMULA
From Colin Barker, May 18 2018: (Start)
G.f.: 39*(6 + x) / ((1 - x)*(1 - 2*x)).
a(n) = 3*a(n-1) - 2*a(n-2) for n>1.
(End)
MAPLE
seq(507*2^n - 273, n = 0 .. 40);
MATHEMATICA
Table[507*2^n-273, {n, 0, 30}] (* Harvey P. Dale, Jul 17 2019 *)
PROG
(PARI) Vec(39*(6 + x) / ((1 - x)*(1 - 2*x)) + O(x^40)) \\ Colin Barker, May 18 2018
CROSSREFS
Sequence in context: A186897 A184450 A338391 * A287878 A252338 A252777
KEYWORD
nonn,easy
AUTHOR
Emeric Deutsch, May 16 2018
STATUS
approved

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Last modified February 23 14:24 EST 2024. Contains 370283 sequences. (Running on oeis4.)