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%I #11 Mar 20 2020 21:05:22
%S 0,0,1,4,17,72,342,1905,12156,89268,738911,6798758,68520038,748502910,
%T 8788173335,110193643134,1468070949946,20694573672876,307578336064984,
%U 4805384561143819,78708210390090371,1348365584611572634,24108682771962822336,449043803118075490633
%N Number of unlabeled connected simple graphs with n nodes of degree 4 or less, except trees and 4-regular graphs.
%C 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 a(n) = A121941(n) - A006820(n) - A000602(n).
%F a(n) = A287424(n) - A000602(n).
%Y Cf. A000602, A006820, A121941, A287424.
%K nonn
%O 1,4
%A _Natan Arie Consigli_, Jul 07 2017
%E a(0) removed and a(16)-a(24) from _Andrew Howroyd_, Mar 20 2020