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) |
|---|---|
| 0 | 3 |
| 1 | 9 |
| 2 | 41 |
| 3 | 225 |
| 4 | 1313 |
| 5 | 7809 |
| 6 | 46721 |
| 7 | 280065 |
| 8 | 1679873 |
| 9 | 10078209 |
| 10 | 60467201 |
| 11 | 362799105 |
| 12 | 2176786433 |
| 13 | 13060702209 |
| 14 | 78364180481 |
| 15 | 470185017345 |
| 16 | 2821109972993 |
| 17 | 16926659575809 |
| 18 | 101559956930561 |
| 19 | 609359740534785 |
| 20 | 3656158441111553 |