a(1) = 1; a(n) is the smallest triangular number > a(n-1) which differs from it at every digit.

Terms

a(0) =1a(1) =3a(2) =6a(3) =10a(4) =21a(5) =36a(6) =45a(7) =66a(8) =78a(9) =91a(10) =105a(11) =210a(12) =325a(13) =406a(14) =528a(15) =630a(16) =703a(17) =820a(18) =903a(19) =1035a(20) =2211a(21) =3003a(22) =4186a(23) =5050a(24) =6105a(25) =7021a(26) =8256a(27) =9045a(28) =10153a(29) =21321