Squarefree triangular numbers.

Terms

a(0) =1a(1) =3a(2) =6a(3) =10a(4) =15a(5) =21a(6) =55a(7) =66a(8) =78a(9) =91a(10) =105a(11) =190a(12) =210a(13) =231a(14) =253a(15) =406a(16) =435a(17) =465a(18) =561a(19) =595a(20) =703a(21) =741a(22) =861a(23) =903a(24) =946a(25) =1081a(26) =1326a(27) =1378a(28) =1653a(29) =1711