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 | 13 |
| 4 | 78 |
| 5 | 612 |
| 6 | 5796 |
| 7 | 64426 |
| 8 | 822470 |
| 9 | 11856945 |
| 10 | 190494094 |
| 11 | 3374719084 |
| 12 | 65351559893 |
| 13 | 1373320643023 |
| 14 | 31124359701926 |
| 15 | 756718320351009 |
| 16 | 19645797269948963 |
| 17 | 542437979097898912 |
| 18 | 15871685747774947593 |
| 19 | 490576250611060132721 |
| 20 | 15972108990755818357442 |