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, 6798758, 68520038, 748502910, 8788173335, 110193643134, 1468070949946, 20694573672876, 307578336064984, 4805384561143819, 78708210390090371, 1348365584611572634, 24108682771962822336, 449043803118075490633

Offset: 1

Author

Natan Arie Consigli, Jul 07 2017

Keywords

• nonn

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.

Crossrefs

Cf. A000602, A006820, A121941, A287424.

Formula

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

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

Extensions

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