Principal diagonal of the convolution array A213561.

Terms

a(0) =1a(1) =18a(2) =109a(3) =407a(4) =1152a(5) =2723a(6) =5670a(7) =10746a(8) =18939a(9) =31504a(10) =49995a(11) =76297a(12) =112658a(13) =161721a(14) =226556a(15) =310692a(16) =418149a(17) =553470a(18) =721753a(19) =928683a(20) =1180564a(21) =1484351a(22) =1847682a(23) =2278910a(24) =2787135a(25) =3382236a(26) =4074903a(27) =4876669a(28) =5799942a(29) =6858037