A289159 Number of unlabeled connected simple graphs with n nodes of degree 4 or less, except trees and 4-regular graphs.

0, 0, 1, 4, 17, 72, 342, 1905, 12156, 89268, 738911, 6798738, 68520038, 748502910, 8788173335, 110193643134, 1468070949946, 20694573672876, 307578336064984, 4805384561143819, 78708210390090371, 1348365584611572634, 24108682771962822336, 449043803118075490633

Offset

1,4

Comments

Also number of saturated cyclic hydrocarbons (cycloalkanes and alkyl cycloalkanes) with n carbon atoms satisfying the octet rule. Stereoisomerism is not taken into account. Some of the drawn structures may or may not exist due to their strained geometries.

Links

Table of n, a(n) for n=1..24.

Formula

a(n) = A121941(n) - A006820(n) - A000602(n).

a(n) = A287424(n) - A000602(n).

Crossrefs

Cf. A000602, A006820, A121941, A287424.

Sequence in context: A113442 A362908 A085732 * A083330 A255632 A255814

Adjacent sequences: A289156 A289157 A289158 * A289160 A289161 A289162

Keyword

nonn

Author

Natan Arie Consigli, Jul 07 2017

Extensions

a(0) removed and a(16)-a(24) from Andrew Howroyd, Mar 20 2020

a(12) corrected by Falk Hüffner, May 21 2026

Status

approved