Smaller of the two successive triangular numbers which differ in the use of only one digit.

Terms

a(0) =0a(1) =1a(2) =3a(3) =10a(4) =15a(5) =21a(6) =45a(7) =105a(8) =136a(9) =190a(10) =210a(11) =231a(12) =325a(13) =435a(14) =465a(15) =780a(16) =1081a(17) =1225a(18) =1485a(19) =1596a(20) =2415a(21) =3081a(22) =4005a(23) =4465a(24) =4560a(25) =5253a(26) =6670a(27) =7021a(28) =7750a(29) =9730