Principal diagonal of the convolution array A213768.

Terms

a(0) =1a(1) =8a(2) =26a(3) =63a(4) =136a(5) =272a(6) =521a(7) =968a(8) =1762a(9) =3159a(10) =5600a(11) =9840a(12) =17169a(13) =29784a(14) =51418a(15) =88399a(16) =151432a(17) =258592a(18) =440345a(19) =747960a(20) =1267586a(21) =2143783a(22) =3618816a(23) =6098208a(24) =10260001a(25) =17236712a(26) =28918106a(27) =48454623a(28) =81093832a(29) =135569264