A290131/2.

Terms

a(0) =0a(1) =1a(2) =6a(3) =20a(4) =48a(5) =102a(6) =184a(7) =317a(8) =506a(9) =772a(10) =1118a(11) =1593a(12) =2180a(13) =2949a(14) =3882a(15) =5011a(16) =6356a(17) =8013a(18) =9922a(19) =12224a(20) =14854a(21) =17878a(22) =21302a(23) =25301a(24) =29748a(25) =34825a(26) =40470a(27) =46800a(28) =53770a(29) =61658