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) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 2 |
| 4 | 6 |
| 5 | 22 |
| 6 | 88 |
| 7 | 372 |
| 8 | 1636 |
| 9 | 7406 |
| 10 | 34276 |
| 11 | 161436 |
| 12 | 771238 |
| 13 | 3728168 |
| 14 | 18201830 |
| 15 | 89622696 |
| 16 | 444533010 |
| 17 | 2219057382 |
| 18 | 11139859864 |
| 19 | 56203325212 |
| 20 | 284828848740 |
| 21 | 1449270351504 |