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 | 15 |
| 4 | 250 |
| 5 | 251 |
| 6 | 3980 |
| 7 | 3981 |
| 8 | 63095 |
| 9 | 999999 |
| 10 | 1000000 |
| 11 | 15848931 |
| 12 | 251188642 |
| 13 | 251188643 |
| 14 | 3981071705 |
| 15 | 63095734447 |
| 16 | 63095734448 |
| 17 | 999999999999 |
| 18 | 1000000000000 |
| 19 | 15848931924610 |
| 20 | 15848931924611 |
| 21 | 251188643150957 |
| 22 | 251188643150958 |
| 23 | 3981071705534972 |
| 24 | 63095734448019324 |