(Largest) diagonal of the Zorach additive triangle A035312.

Terms

a(0) =1a(1) =3a(2) =9a(3) =26a(4) =66a(5) =154a(6) =346a(7) =771a(8) =1726a(9) =3887a(10) =8768a(11) =19700a(12) =43890a(13) =96717a(14) =210665a(15) =453893a(16) =968903a(17) =2053260a(18) =4328489a(19) =9093971a(20) =19068611a(21) =39943689a(22) =83628399a(23) =175018523a(24) =366081209a(25) =765102907a(26) =1597315656a(27) =3330380593a(28) =6933810145