Principal diagonal of the convolution array A213564.

Terms

a(0) =1a(1) =21a(2) =127a(3) =467a(4) =1302a(5) =3038a(6) =6258a(7) =11754a(8) =20559a(9) =33979a(10) =53625a(11) =81445a(12) =119756a(13) =171276a(14) =239156a(15) =327012a(16) =438957a(17) =579633a(18) =754243a(19) =968583a(20) =1229074a(21) =1542794a(22) =1917510a(23) =2361710a(24) =2884635a(25) =3496311a(26) =4207581a(27) =5030137a(28) =5976552a(29) =7060312