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) |
|---|---|
| 1 | 1 |
| 2 | 9 |
| 3 | 80 |
| 4 | 654 |
| 5 | 6264 |
| 6 | 59760 |
| 7 | 665160 |
| 8 | 7565040 |
| 9 | 96929280 |
| 10 | 1286046720 |
| 11 | 18976083840 |
| 12 | 286363123200 |
| 13 | 4775047200000 |
| 14 | 81792956044800 |
| 15 | 1515077749785600 |
| 16 | 28898470215014400 |
| 17 | 594066352700620800 |
| 18 | 12467555729620992000 |
| 19 | 280797084422959104000 |
| 20 | 6460327992512249856000 |
| 21 | 157769680941941612544000 |