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 | 3 |
| 2 | 24 |
| 3 | 168 |
| 4 | 1155 |
| 5 | 7920 |
| 6 | 54288 |
| 7 | 372099 |
| 8 | 2550408 |
| 9 | 17480760 |
| 10 | 119814915 |
| 11 | 821223648 |
| 12 | 5628750624 |
| 13 | 38580030723 |
| 14 | 264431464440 |
| 15 | 1812440220360 |
| 16 | 12422650078083 |
| 17 | 85146110326224 |
| 18 | 583600122205488 |
| 19 | 4000054745112195 |
| 20 | 27416783093579880 |
| 21 | 187917426909946968 |