a(n) = A306302(n)/2.

Terms

a(0) =0a(1) =2a(2) =8a(3) =23a(4) =52a(5) =107a(6) =190a(7) =324a(8) =514a(9) =781a(10) =1128a(11) =1604a(12) =2192a(13) =2962a(14) =3896a(15) =5026a(16) =6372a(17) =8030a(18) =9940a(19) =12243a(20) =14874a(21) =17899a(22) =21324a(23) =25324a(24) =29772a(25) =34850a(26) =40496a(27) =46827a(28) =53798a(29) =61687