This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
For n=3, the first string of 3 digits to repeat in Pi is A197123(3) = 592 and it had first occurred at position a(3) = 4,
Pi = 3.141592 ... 592...
^ ^
position 4 61
a(2) = 4392366484 because 4392366484 is the first 10-digit number to appear 2 times in the decimal expansion of Pi.
We need 3 digits (141) to find the first digit to repeat (the repeated digit is 1). We need 22 digits (1415926535897932384626) to find the first 2 digit repeat (the repeated 2-digit substring is 26).
a(2) = 18 because 18 is the first 2-digit number to repeat in the decimal expansion of e = 2.7(18)28(18)... 2 appears at positions 0 and 4. 18 appears at positions 2 and 6. 182 appears at positions 2 and 6. 1828 appears at positions 2 and 6. 98793 appears at positions 478 and 494. 987931 appears at positions 478 and 494. 4349076 appears at positions 170 and 2731. ...
a(1) = 1, because '1' is the first 1-digit string appearing 1 time (at position 1); a(2) = 26, because '26' is the first 2-digit string appearing 2 times (at positions 6 and 21); a(3) = 446, because '446' is the first 3-digit string appearing 3 times (at positions 125, 182 and 217); and so on.
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