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 | 2 |
| 2 | 24 |
| 3 | 180 |
| 4 | 7420 |
| 5 | 33264 |
| 6 | 991848 |
| 7 | 3938220 |
| 8 | 103832872 |
| 9 | 389398464 |
| 10 | 9620555000 |
| 11 | 34901442000 |
| 12 | 828288777420 |
| 13 | 2940343837200 |
| 14 | 67898251759800 |
| 15 | 237371722628040 |
| 16 | 5373868753340880 |
| 17 | 97581248745060600 |
| 18 | 335240928272918304 |
| 19 | 7415892272293658608 |
| 20 | 25286571126114014640 |
| 21 | 553714770886681187168 |