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.
| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 21 |
| 4 | 463 |
| 5 | 464 |
| 6 | 9999 |
| 7 | 10000 |
| 8 | 215443 |
| 9 | 4641588 |
| 10 | 99999999 |
| 11 | 100000000 |
| 12 | 2154434689 |
| 13 | 2154434690 |
| 14 | 46415888335 |
| 15 | 46415888336 |
| 16 | 999999999999 |
| 17 | 1000000000000 |
| 18 | 21544346900318 |
| 19 | 464158883361277 |
| 20 | 9999999999999999 |
| 21 | 10000000000000000 |
| 22 | 215443469003188371 |
| 23 | 215443469003188372 |