First differences give (essentially) A028242.

Terms

a(0) =3a(1) =9a(2) =17a(3) =29a(4) =44a(5) =64a(6) =88a(7) =118a(8) =153a(9) =195a(10) =243a(11) =299a(12) =362a(13) =434a(14) =514a(15) =604a(16) =703a(17) =813a(18) =933a(19) =1065a(20) =1208a(21) =1364a(22) =1532a(23) =1714a(24) =1909a(25) =2119a(26) =2343a(27) =2583a(28) =2838a(29) =3110