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 | 1 |
| 2 | 1 |
| 3 | 3 |
| 4 | 1 |
| 5 | 15 |
| 6 | 45 |
| 7 | 21 |
| 8 | 315 |
| 9 | 2835 |
| 10 | 4725 |
| 11 | 22275 |
| 12 | 93555 |
| 13 | 2027025 |
| 14 | 42567525 |
| 15 | 638512875 |
| 16 | 212837625 |
| 17 | 2170943775 |
| 18 | 13956067125 |
| 19 | 618718975875 |
| 20 | 9280784638125 |
| 21 | 14992036723125 |
| 22 | 7522320180375 |
| 23 | 49308808782358125 |
| 24 | 147926426347074375 |