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 | 2 |
| 3 | 6 |
| 4 | 18 |
| 5 | 66 |
| 6 | 396 |
| 7 | 2052 |
| 8 | 12636 |
| 9 | 91548 |
| 10 | 625176 |
| 11 | 4673736 |
| 12 | 43575192 |
| 13 | 377205336 |
| 14 | 3624289488 |
| 15 | 38829340656 |
| 16 | 397695226896 |
| 17 | 4338579616272 |
| 18 | 54018173703456 |
| 19 | 641634784488288 |
| 20 | 8208962893594656 |
| 21 | 113809776294348576 |
| 22 | 1526808627197721792 |
| 23 | 21533423236302943296 |