This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A289159 #11 Mar 20 2020 21:05:22 %S A289159 0,0,1,4,17,72,342,1905,12156,89268,738911,6798758,68520038,748502910, %T A289159 8788173335,110193643134,1468070949946,20694573672876,307578336064984, %U A289159 4805384561143819,78708210390090371,1348365584611572634,24108682771962822336,449043803118075490633 %N A289159 Number of unlabeled connected simple graphs with n nodes of degree 4 or less, except trees and 4-regular graphs. %C A289159 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. %F A289159 a(n) = A121941(n) - A006820(n) - A000602(n). %F A289159 a(n) = A287424(n) - A000602(n). %Y A289159 Cf. A000602, A006820, A121941, A287424. %K A289159 nonn %O A289159 1,4 %A A289159 _Natan Arie Consigli_, Jul 07 2017 %E A289159 a(0) removed and a(16)-a(24) from _Andrew Howroyd_, Mar 20 2020