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 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 27 |
| 5 | 248 |
| 6 | 2822 |
| 7 | 37820 |
| 8 | 578915 |
| 9 | 9918924 |
| 10 | 187558638 |
| 11 | 3873705128 |
| 12 | 86692262942 |
| 13 | 2089070253556 |
| 14 | 53925007946392 |
| 15 | 1484529898970648 |
| 16 | 43421639185592359 |
| 17 | 1344923240469786704 |
| 18 | 43981996770022295714 |
| 19 | 1514531024603022580980 |
| 20 | 54783958839510354056018 |
| 21 | 2077007174758224026216216 |