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 | 2 |
| 3 | 7 |
| 4 | 35 |
| 5 | 237 |
| 6 | 2040 |
| 7 | 21255 |
| 8 | 259591 |
| 9 | 3633549 |
| 10 | 57320398 |
| 11 | 1005959831 |
| 12 | 19436938571 |
| 13 | 409965565469 |
| 14 | 9372278051700 |
| 15 | 230832086585495 |
| 16 | 6093185704307967 |
| 17 | 171604903098322813 |
| 18 | 5136091192685429770 |
| 19 | 162792009969153667111 |
| 20 | 5447239135976543715731 |
| 21 | 191888373741260775025741 |