Smallest number k such that no n-digit triangular number begins with k.

Terms

a(0) =2a(1) =8a(2) =11a(3) =60a(4) =103a(5) =532a(6) =1002a(7) =5100a(8) =10002a(9) =50316a(10) =100002a(11) =501000a(12) =1000000a(13) =5003162a(14) =10000000a(15) =50010000a(16) =100000002a(17) =500031623a(18) =1000000002a(19) =5000100000a(20) =10000000000a(21) =50000316228a(22) =100000000002a(23) =500001000000