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 | 1 |
| 4 | 5 |
| 5 | 68 |
| 6 | 403 |
| 7 | 7257 |
| 8 | 61686 |
| 9 | 1174434 |
| 10 | 13810620 |
| 11 | 335547727 |
| 12 | 3783688286 |
| 13 | 124486381056 |
| 14 | 1935430229612 |
| 15 | 55798127869680 |
| 16 | 1058567311736669 |
| 17 | 39819079382937334 |
| 18 | 717447490866241055 |
| 19 | 32064848897165970340 |
| 20 | 666062878027691348450 |
| 21 | 28916070816360797805534 |