Triangular numbers of the form 6*k.

Terms

a(0) =0a(1) =6a(2) =36a(3) =66a(4) =78a(5) =120a(6) =210a(7) =276a(8) =300a(9) =378a(10) =528a(11) =630a(12) =666a(13) =780a(14) =990a(15) =1128a(16) =1176a(17) =1326a(18) =1596a(19) =1770a(20) =1830a(21) =2016a(22) =2346a(23) =2556a(24) =2628a(25) =2850a(26) =3240a(27) =3486a(28) =3570a(29) =3828