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 | 5 |
| 4 | 33 |
| 5 | 265 |
| 6 | 2505 |
| 7 | 27261 |
| 8 | 335757 |
| 9 | 4617461 |
| 10 | 70138689 |
| 11 | 1166295457 |
| 12 | 21072290241 |
| 13 | 411069239997 |
| 14 | 8611025176533 |
| 15 | 192788027607293 |
| 16 | 4594027768539585 |
| 17 | 116093660372707273 |
| 18 | 3101080076109154137 |
| 19 | 87305805274735566669 |