%I #6 Dec 01 2021 12:38:28
%S 4,16,46,106,208,364,586,886,1276,1768,2374,3106,3976,4996,6178,7534,
%T 9076,10816,12766,14938,17344,19996,22906,26086,29548,33304,37366,
%U 41746,46456,51508,56914,62686,68836,75376,82318,89674,97456,105676,114346
%N The number of trisubstitution products with composition C_n H_(2n-1) X_2 Y.
%C See the paper by Valentin Vankov Iliev for details.
%H Valentin Vankov Iliev, <a href="https://doi.org/10.1007/s10910-009-9534-4">A mathematical characterization of the groups of substitution isomerism of the linear alkanes</a>, J. Math. Chem. 47 (2010), 52-61.
%H <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (4,-6,4,-1).
%F a(n) = (2 n^3 - 9 n^2 + 19 n - 14) where n is the number of carbons.
%F G.f.: 2*x^2*(2+3*x^2+x^3)/(x-1)^4. - _R. J. Mathar_, Apr 28 2009
%e The number of trisubstitution products with composition C_n H_(2n-1) X_2 Y for n = 10 is 1276.
%Y Cf. A002522, A033816, A159938, A159941.
%K nonn,easy
%O 2,1
%A _Parthasarathy Nambi_, Apr 26 2009
%E More terms from _R. J. Mathar_, Apr 28 2009