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 | 2 |
| 2 | 6 |
| 3 | 22 |
| 4 | 98 |
| 5 | 516 |
| 6 | 3172 |
| 7 | 22436 |
| 8 | 180252 |
| 9 | 1624888 |
| 10 | 16258376 |
| 11 | 178877832 |
| 12 | 2146674136 |
| 13 | 27907332272 |
| 14 | 390705042288 |
| 15 | 5860585983856 |
| 16 | 93769421948432 |
| 17 | 1594080384922656 |
| 18 | 28693447925921632 |
| 19 | 545175515402212448 |
| 20 | 10903510331802913056 |
| 21 | 228973717087813867072 |