Number of trees with n nodes and 4 leaves.

Terms

a(0) =1a(1) =2a(2) =4a(3) =8a(4) =14a(5) =23a(6) =36a(7) =54a(8) =78a(9) =110a(10) =150a(11) =201a(12) =264a(13) =341a(14) =433a(15) =544a(16) =674a(17) =827a(18) =1004a(19) =1209a(20) =1443a(21) =1711a(22) =2013a(23) =2355a(24) =2738a(25) =3167a(26) =3643a(27) =4173a(28) =4757a(29) =5402