6 times triangular numbers: a(n) = 3*n*(n+1).

Terms

a(0) =0a(1) =6a(2) =18a(3) =36a(4) =60a(5) =90a(6) =126a(7) =168a(8) =216a(9) =270a(10) =330a(11) =396a(12) =468a(13) =546a(14) =630a(15) =720a(16) =816a(17) =918a(18) =1026a(19) =1140a(20) =1260a(21) =1386a(22) =1518a(23) =1656a(24) =1800a(25) =1950a(26) =2106a(27) =2268a(28) =2436a(29) =2610