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 | 1 |
| 2 | 4 |
| 3 | 22 |
| 4 | 140 |
| 5 | 992 |
| 6 | 7584 |
| 7 | 61420 |
| 8 | 520320 |
| 9 | 4570292 |
| 10 | 41354416 |
| 11 | 383609434 |
| 12 | 3634231140 |
| 13 | 35059333218 |
| 14 | 343580813492 |
| 15 | 3413862553800 |
| 16 | 34336784362232 |
| 17 | 349131316634164 |
| 18 | 3584622273967324 |
| 19 | 37128374058146138 |
| 20 | 387630493693010928 |
| 21 | 4076329834240413392 |
| 22 | 43150916852592230992 |