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 | 2 |
| 3 | 6 |
| 4 | 18 |
| 5 | 30 |
| 6 | 270 |
| 7 | 606 |
| 8 | 123120 |
| 9 | 888456 |
| 10 | 23070450 |
| 11 | 238550160 |
| 12 | 8282903640 |
| 13 | 72789145650 |
| 14 | 15681266370000 |
| 15 | 18216437241240 |