Apply partial sum operator thrice to binary rooted tree numbers.

Terms

a(0) =1a(1) =4a(2) =11a(3) =25a(4) =51a(5) =98a(6) =182a(7) =331a(8) =595a(9) =1063a(10) =1894a(11) =3373a(12) =6010a(13) =10719a(14) =19139a(15) =34208a(16) =61195a(17) =109551a(18) =196228a(19) =351636a(20) =630330a(21) =1130181a(22) =2026775a(23) =3635128a(24) =6520408a(25) =11696591a(26) =20982875a(27) =37643135a(28) =67533204