1, together with numbers of the form k*(k+1) or k*(k+2), k > 0.

Terms

a(0) =1a(1) =2a(2) =3a(3) =6a(4) =8a(5) =12a(6) =15a(7) =20a(8) =24a(9) =30a(10) =35a(11) =42a(12) =48a(13) =56a(14) =63a(15) =72a(16) =80a(17) =90a(18) =99a(19) =110a(20) =120a(21) =132a(22) =143a(23) =156a(24) =168a(25) =182a(26) =195a(27) =210a(28) =224a(29) =240