

A121254


Number of conjugated cycles composed of six carbons in (n,n)nanotubes in terms of the number of naphthalene units.


0



4, 16, 60, 208, 680, 2136, 6524, 19520, 57492, 167240, 481624, 1375536
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OFFSET

1,1


COMMENTS

See Table 2 on page 412 of Lukovits and Janezic paper for details.


LINKS

Table of n, a(n) for n=1..12.
I. Lukovits et al. Enumeration of conjugated circuits in nanotubes, J. Chem. Inf. Comput. Sci. 44 (2004), 410414.
Index entries for linear recurrences with constant coefficients, signature (6, 11, 6, 1).


FORMULA

Conjecture: a(n)=6a(n1)11a(n2)+6a(n3)a(n4)=4*A117202(n). G.f.: 4*x*(12*x+2*x^2)/(x^23*x+1)^2. [From R. J. Mathar, Mar 18 2009]


EXAMPLE

If n=5 then the number of conjugated cycles composed of six carbons in (n,n)nanotubes is 680 which is the fifth term in the sequence. Here n is the number of naphthalene units.


CROSSREFS

Sequence in context: A265955 A217374 A055295 * A261519 A262591 A119827
Adjacent sequences: A121251 A121252 A121253 * A121255 A121256 A121257


KEYWORD

nonn


AUTHOR

Parthasarathy Nambi, Aug 22 2006


STATUS

approved



