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 | 6 |
| 3 | 20 |
| 4 | 128 |
| 5 | 800 |
| 6 | 7252 |
| 7 | 78063 |
| 8 | 1059783 |
| 9 | 17120947 |
| 10 | 324989973 |
| 11 | 7091405557 |
| 12 | 175501697220 |
| 13 | 4869895326986 |
| 14 | 150149181850071 |
| 15 | 5105014674244446 |
| 16 | 190170557622677435 |
| 17 | 7718536219718200652 |
| 18 | 339658159537506154540 |
| 19 | 16135241804080190069164 |
| 20 | 824225772252119571338949 |