Main diagonal of array in A358298.

Terms

a(0) =2a(1) =6a(2) =20a(3) =60a(4) =124a(5) =252a(6) =388a(7) =652a(8) =924a(9) =1332a(10) =1748a(11) =2428a(12) =2988a(13) =3948a(14) =4788a(15) =5908a(16) =7028a(17) =8692a(18) =9964a(19) =12052a(20) =13748a(21) =16004a(22) =18124a(23) =21204a(24) =23476a(25) =26996a(26) =29972a(27) =33788a(28) =37196a(29) =42124