Oblong (or promic, pronic, or heteromecic) numbers: a(n) = n*(n+1).

Terms

a(0) =0a(1) =2a(2) =6a(3) =12a(4) =20a(5) =30a(6) =42a(7) =56a(8) =72a(9) =90a(10) =110a(11) =132a(12) =156a(13) =182a(14) =210a(15) =240a(16) =272a(17) =306a(18) =342a(19) =380a(20) =420a(21) =462a(22) =506a(23) =552a(24) =600a(25) =650a(26) =702a(27) =756a(28) =812a(29) =870