The number of trisubstitution products with composition C_n H_(2n-1) X_2 Y.

Terms

a(0) =4a(1) =16a(2) =46a(3) =106a(4) =208a(5) =364a(6) =586a(7) =886a(8) =1276a(9) =1768a(10) =2374a(11) =3106a(12) =3976a(13) =4996a(14) =6178a(15) =7534a(16) =9076a(17) =10816a(18) =12766a(19) =14938a(20) =17344a(21) =19996a(22) =22906a(23) =26086a(24) =29548a(25) =33304a(26) =37366a(27) =41746a(28) =46456a(29) =51508