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 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 6 |
| 4 | 66 |
| 5 | 772 |
| 6 | 6760 |
| 7 | 60122 |
| 8 | 552930 |
| 9 | 4887052 |
| 10 | 42365416 |
| 11 | 361418592 |
| 12 | 3063883318 |
| 13 | 25819450218 |
| 14 | 215875963118 |
| 15 | 1793852851690 |
| 16 | 14833014554258 |
| 17 | 122147248758898 |
| 18 | 1002084660185318 |
| 19 | 8192705916505028 |
| 20 | 66777880125812344 |
| 21 | 542833111487459532 |
| 22 | 4401913323626254612 |
| 23 | 35616479684643020150 |