Number of monocyclic skeletons with n carbon atoms and a ring size of 4.

Terms

a(0) =1a(1) =1a(2) =4a(3) =8a(4) =24a(5) =55a(6) =147a(7) =365a(8) =954a(9) =2431a(10) =6327a(11) =16369a(12) =42743a(13) =111595a(14) =292849a(15) =769805a(16) =2030456a(17) =5366844a(18) =14222475a(19) =37768154a(20) =100510364a(21) =267987501a(22) =715847932a(23) =1915406263a(24) =5133382014a(25) =13778469949a(26) =37035674682a(27) =99683747508a(28) =268647638770a(29) =724879674667