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 | 3 |
| 3 | 15 |
| 4 | 97 |
| 5 | 745 |
| 6 | 6571 |
| 7 | 65359 |
| 8 | 723969 |
| 9 | 8842257 |
| 10 | 118091251 |
| 11 | 1712261551 |
| 12 | 26786070433 |
| 13 | 449634481465 |
| 14 | 8059974923547 |
| 15 | 153634497337455 |
| 16 | 3102367733191681 |
| 17 | 66145005096272929 |
| 18 | 1484586887025099619 |
| 19 | 34983117545622446287 |
| 20 | 863397428225495045601 |
| 21 | 22269844592814969946761 |