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 | 5 |
| 3 | 23 |
| 4 | 134 |
| 5 | 814 |
| 6 | 6324 |
| 7 | 50028 |
| 8 | 475824 |
| 9 | 4806576 |
| 10 | 54597600 |
| 11 | 644119200 |
| 12 | 8847100800 |
| 13 | 121718332800 |
| 14 | 1853505158400 |
| 15 | 29894856364800 |
| 16 | 518855607244800 |
| 17 | 9197155541145600 |
| 18 | 179420609436364800 |
| 19 | 3537039053405491200 |
| 20 | 75849875285280768000 |
| 21 | 1670700245252548608000 |