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) |
|---|---|
| 3 | 1 |
| 4 | 8 |
| 5 | 80 |
| 6 | 860 |
| 7 | 10290 |
| 8 | 136080 |
| 9 | 1977360 |
| 10 | 31365600 |
| 11 | 539847000 |
| 12 | 10026139200 |
| 13 | 199937337600 |
| 14 | 4262167509600 |
| 15 | 96744738090000 |
| 16 | 2329950823200000 |
| 17 | 59348032327584000 |
| 18 | 1594257675506496000 |
| 19 | 45047749044458160000 |
| 20 | 1335740755933584000000 |
| 21 | 41473196779273459200000 |