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 | 1 |
| 2 | 4 |
| 3 | 16 |
| 4 | 104 |
| 5 | 704 |
| 6 | 6368 |
| 7 | 58752 |
| 8 | 662272 |
| 9 | 7802880 |
| 10 | 106639872 |
| 11 | 1511241216 |
| 12 | 24062834688 |
| 13 | 398765162496 |
| 14 | 7252942872576 |
| 15 | 137324083666944 |
| 16 | 2804224273514496 |
| 17 | 59594575901687808 |
| 18 | 1352293406316822528 |
| 19 | 31831016595468189696 |