A diagonal of A036969.

Terms

a(0) =0a(1) =1a(2) =21a(3) =147a(4) =627a(5) =2002a(6) =5278a(7) =12138a(8) =25194a(9) =48279a(10) =86779a(11) =148005a(12) =241605a(13) =380016a(14) =578956a(15) =857956a(16) =1240932a(17) =1756797a(18) =2440113a(19) =3331783a(20) =4479783a(21) =5939934a(22) =7776714a(23) =10064110a(24) =12886510a(25) =16339635a(26) =20531511a(27) =25583481a(28) =31631257a(29) =38826012