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 | 138 |
| 5 | 2021 |
| 6 | 43581 |
| 7 | 1295493 |
| 8 | 50752145 |
| 9 | 2533755933 |
| 10 | 157055247261 |
| 11 | 11836611005031 |
| 12 | 1066129321651668 |
| 13 | 113117849882149725 |
| 14 | 13965580274228976213 |
| 15 | 1985189312618723797371 |
| 16 | 321932406123733248625851 |
| 17 | 59079829666712346141491403 |
| 18 | 12182062872168618012045410805 |