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 | 0 |
| 2 | 0 |
| 3 | 3 |
| 4 | 0 |
| 5 | 15 |
| 6 | 45 |
| 7 | 63 |
| 8 | 1260 |
| 9 | 1515 |
| 10 | 25515 |
| 11 | 104973 |
| 12 | 510345 |
| 13 | 5679765 |
| 14 | 17252235 |
| 15 | 263214318 |
| 16 | 1207222380 |
| 17 | 11863296915 |
| 18 | 101718989235 |
| 19 | 630468648873 |
| 20 | 8281982665215 |
| 21 | 48583038314415 |
| 22 | 656006633919945 |
| 23 | 5122900223419938 |
| 24 | 54304561161840825 |
| 25 | 605082149235374265 |