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) |
|---|---|
| 2 | 1 |
| 3 | 9 |
| 4 | 59 |
| 5 | 450 |
| 6 | 3394 |
| 7 | 30912 |
| 8 | 293292 |
| 9 | 3032208 |
| 10 | 36290736 |
| 11 | 433762560 |
| 12 | 5925016800 |
| 13 | 83648747520 |
| 14 | 1335385128960 |
| 15 | 20323375994880 |
| 16 | 376785057196800 |
| 17 | 6493118120294400 |
| 18 | 132672192555571200 |
| 19 | 2513351450024755200 |
| 20 | 56577426980420505600 |
| 21 | 1188283280226545664000 |
| 22 | 29682641812682686464000 |
| 23 | 658094690655791972352000 |