Triangular numbers that contain exactly 2 different digits.

Terms

a(0) =10a(1) =15a(2) =21a(3) =28a(4) =36a(5) =45a(6) =78a(7) =91a(8) =171a(9) =300a(10) =595a(11) =990a(12) =1711a(13) =2211a(14) =3003a(15) =5050a(16) =5151a(17) =5565a(18) =5995a(19) =6555a(20) =8778a(21) =10011a(22) =66066a(23) =222111a(24) =255255a(25) =333336a(26) =500500a(27) =600060a(28) =828828a(29) =887778