Triangular numbers which become primes when their rightmost digit is removed.

Terms

a(0) =21a(1) =28a(2) =36a(3) =55a(4) =78a(5) =136a(6) =171a(7) =190a(8) =231a(9) =378a(10) =435a(11) =595a(12) =1035a(13) =1275a(14) =1378a(15) =2278a(16) =2415a(17) =2775a(18) =4095a(19) =5778a(20) =5995a(21) =7875a(22) =8778a(23) =10878a(24) =11175a(25) =11935a(26) =14535a(27) =14878a(28) =21115a(29) =26335