A159938 The number of homogeneous trisubstituted linear alkanes.

2, 6, 16, 36, 70, 122, 196, 296, 426, 590, 792, 1036, 1326, 1666, 2060, 2512, 3026, 3606, 4256, 4980, 5782, 6666, 7636, 8696, 9850, 11102, 12456, 13916, 15486, 17170, 18972, 20896, 22946, 25126, 27440, 29892, 32486

Offset

2,1

Comments

See the paper by Valentin Vankov Iliev for details.

This sequence is related to A152947 by a(n) = (n-1)*A152947(n) + sum( A152947(i), i=1..n-1 ). - Bruno Berselli, Dec 19 2013

Links

Table of n, a(n) for n=2..38.

Valentin Vankov Iliev, A mathematical characterization of the groups of substitution isomerism of the linear alkanes, J. Math. Chem. 47 (2010), 52-61.

Index entries for linear recurrences with constant coefficients, signature (4,-6,4,-1).

Formula

a(n) = (1/3)*(2*n^3 - 9*n^2 + 19*n - 12), where n is the number of carbons.

a(n) = 2*A081489(n-1) = (n-1)*(2*n^2-7*n+12)/3. - R. J. Mathar, Apr 28 2009

G.f.: 2*x^2*(1-x+2*x^2)/(1-x)^4. - Colin Barker, Aug 06 2012

Example

The number of homogeneous trisubstituted linear alkane with ten carbon atoms is 426.

Crossrefs

Cf. A002522, A033816, A081489, A152947, A159940, A159941.

Sequence in context: A330884 A060354 A140131 * A325743 A254119 A145126

Adjacent sequences: A159935 A159936 A159937 * A159939 A159940 A159941

Keyword

nonn,easy

Author

Parthasarathy Nambi, Apr 26 2009

Extensions

More terms from Colin Barker, Aug 06 2012

Status

approved