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 | 1 |
| 1 | 3 |
| 2 | 19 |
| 3 | 117 |
| 4 | 721 |
| 5 | 4443 |
| 6 | 27379 |
| 7 | 168717 |
| 8 | 1039681 |
| 9 | 6406803 |
| 10 | 39480499 |
| 11 | 243289797 |
| 12 | 1499219281 |
| 13 | 9238605483 |
| 14 | 56930852179 |
| 15 | 350823718557 |
| 16 | 2161873163521 |
| 17 | 13322062699683 |
| 18 | 82094249361619 |
| 19 | 505887558869397 |
| 20 | 3117419602578001 |
| 21 | 19210405174337403 |
| 22 | 118379850648602419 |