Apply partial sum operator twice to binary rooted tree numbers.

Terms

a(0) =1a(1) =3a(2) =7a(3) =14a(4) =26a(5) =47a(6) =84a(7) =149a(8) =264a(9) =468a(10) =831a(11) =1479a(12) =2637a(13) =4709a(14) =8420a(15) =15069a(16) =26987a(17) =48356a(18) =86677a(19) =155408a(20) =278694a(21) =499851a(22) =896594a(23) =1608353a(24) =2885280a(25) =5176183a(26) =9286284a(27) =16660260a(28) =29890069a(29) =53626053