Number of mobiles (circular rooted trees) with n nodes and 4 leaves.

Terms

a(0) =1a(1) =4a(2) =16a(3) =46a(4) =118a(5) =260a(6) =527a(7) =985a(8) =1741a(9) =2918a(10) =4701a(11) =7299a(12) =11004a(13) =16142a(14) =23148a(15) =32502a(16) =44823a(17) =60786a(18) =81238a(19) =107098a(20) =139492a(21) =179632a(22) =228979a(23) =289097a(24) =361841a(25) =449188a(26) =553453a(27) =677093a(28) =822954a(29) =994044