9 times the triangular numbers A000217.

Terms

a(0) =0a(1) =9a(2) =27a(3) =54a(4) =90a(5) =135a(6) =189a(7) =252a(8) =324a(9) =405a(10) =495a(11) =594a(12) =702a(13) =819a(14) =945a(15) =1080a(16) =1224a(17) =1377a(18) =1539a(19) =1710a(20) =1890a(21) =2079a(22) =2277a(23) =2484a(24) =2700a(25) =2925a(26) =3159a(27) =3402a(28) =3654a(29) =3915