63.
Exploring The Curiously Fascinating Integer Sequence 1,12,123,1234,12345,123456, 1234567,12345678,123456789, 1234567891,12345678912, 123456789123,. . .
机译:探索令人着迷的整数序列1,12,123,1234,12345,123456,1234567,12345678,123456789,1234567891,12345678912,123456789123。 。 。