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 | 3 |
| 2 | 9 |
| 3 | 87 |
| 4 | 177 |
| 5 | 993 |
| 6 | 10833 |
| 7 | 35619 |
| 8 | 219873 |
| 9 | 2083713 |
| 10 | 8710539 |
| 11 | 55644339 |
| 12 | 473819481 |
| 13 | 2320792659 |
| 14 | 15120204297 |
| 15 | 119105713827 |
| 16 | 650725327233 |
| 17 | 4293779332929 |
| 18 | 32065818855387 |
| 19 | 188739799967427 |
| 20 | 1256510215733187 |
| 21 | 9061494550445907 |