Numbers of the form k*(k+1)/6 for k = 2 or 3 modulo 6.

Terms

a(0) =1a(1) =2a(2) =12a(3) =15a(4) =35a(5) =40a(6) =70a(7) =77a(8) =117a(9) =126a(10) =176a(11) =187a(12) =247a(13) =260a(14) =330a(15) =345a(16) =425a(17) =442a(18) =532a(19) =551a(20) =651a(21) =672a(22) =782a(23) =805a(24) =925a(25) =950a(26) =1080a(27) =1107a(28) =1247a(29) =1276