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 | 24 |
| 5 | 118 |
| 6 | 684 |
| 7 | 4548 |
| 8 | 34036 |
| 9 | 282696 |
| 10 | 2577936 |
| 11 | 25589100 |
| 12 | 274539856 |
| 13 | 3164909164 |
| 14 | 39006958856 |
| 15 | 511759353776 |
| 16 | 7120140764224 |
| 17 | 104703385864788 |
| 18 | 1622530610142744 |
| 19 | 26425922582118000 |
| 20 | 451264786489454168 |
| 21 | 8062192403534869432 |
| 22 | 150395837509736576208 |