Even triangular numbers.

Terms

a(0) =0a(1) =6a(2) =10a(3) =28a(4) =36a(5) =66a(6) =78a(7) =120a(8) =136a(9) =190a(10) =210a(11) =276a(12) =300a(13) =378a(14) =406a(15) =496a(16) =528a(17) =630a(18) =666a(19) =780a(20) =820a(21) =946a(22) =990a(23) =1128a(24) =1176a(25) =1326a(26) =1378a(27) =1540a(28) =1596a(29) =1770