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) |
|---|---|
| 2 | 1 |
| 3 | 3 |
| 4 | 15 |
| 5 | 55 |
| 6 | 231 |
| 7 | 903 |
| 8 | 3655 |
| 9 | 14535 |
| 10 | 58311 |
| 11 | 232903 |
| 12 | 932295 |
| 13 | 3727815 |
| 14 | 14913991 |
| 15 | 59650503 |
| 16 | 238612935 |
| 17 | 954429895 |
| 18 | 3817763271 |
| 19 | 15270965703 |
| 20 | 61084037575 |
| 21 | 244335800775 |
| 22 | 977343902151 |
| 23 | 3909374210503 |
| 24 | 15637499638215 |