OFFSET
2,1
COMMENTS
See the paper by Valentin Vankov Iliev for details.
LINKS
V. V. Iliev, A mathematical characterization of the groups of substitution isomerism of the linear alkanes, J. Math. Chem. 47 (2010), p 52-61.
Index entries for linear recurrences with constant coefficients, signature (4,-6,4,-1).
FORMULA
a(n) = (4*n^3 - 18*n^2 + 38*n - 28) where n is the number of carbons.
a(n) = 2*A159940(n). - R. J. Mathar, Jul 08 2009
G.f.: 4*x^2*(2+3*x^2+x^3)/(1-x)^4. - Colin Barker, Aug 07 2012
a(n) = 4*a(n-1)-6*a(n-2)+4*a(n-3)-a(n-4). - Wesley Ivan Hurt, May 28 2021
EXAMPLE
The number of trisubstituted linear decane (n = 10) is 2552.
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Parthasarathy Nambi, Apr 26 2009
STATUS
approved