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) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 10 |
| 3 | 84 |
| 4 | 852 |
| 5 | 11580 |
| 6 | 197640 |
| 7 | 4314240 |
| 8 | 100855440 |
| 9 | 3342895920 |
| 10 | 98070406560 |
| 11 | 4652556511680 |
| 12 | 163444377096000 |
| 13 | 10568979882901440 |
| 14 | 431650452829115520 |
| 15 | 36599310178253222400 |
| 16 | 1702185892636880851200 |
| 17 | 183500657952824967955200 |
| 18 | 9569677207227878912371200 |