Triangular numbers whose digit reversal is a semiprime (A001358).

Terms

a(0) =6a(1) =15a(2) =28a(3) =55a(4) =78a(5) =105a(6) =120a(7) =190a(8) =496a(9) =780a(10) =903a(11) =946a(12) =1176a(13) =1225a(14) =1275a(15) =1540a(16) =1653a(17) =1770a(18) =1830a(19) =1891a(20) =2080a(21) =3081a(22) =3403a(23) =3486a(24) =3570a(25) =3741a(26) =3916a(27) =4186a(28) =4753a(29) =5050