A121254 Number of conjugated cycles composed of six carbons in (n,n)-nanotubes in terms of the number of naphthalene units.
4, 16, 60, 208, 680, 2136, 6524, 19520, 57492, 167240, 481624, 1375536
Offset: 1
Keywords
Examples
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.
Links
- I. Lukovits et al. Enumeration of conjugated circuits in nanotubes, J. Chem. Inf. Comput. Sci. 44 (2004), 410-414.
- Index entries for linear recurrences with constant coefficients, signature (6, -11, 6, -1).
Formula
Conjecture: a(n)=6a(n-1)-11a(n-2)+6a(n-3)-a(n-4)=4*A117202(n). G.f.: 4*x*(1-2*x+2*x^2)/(x^2-3*x+1)^2. [From R. J. Mathar, Mar 18 2009]
Comments