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 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 3 |
| 5 | 12 |
| 6 | 62 |
| 7 | 393 |
| 8 | 2862 |
| 9 | 23714 |
| 10 | 220205 |
| 11 | 2264965 |
| 12 | 25561752 |
| 13 | 314044379 |
| 14 | 4172303889 |
| 15 | 59604341272 |
| 16 | 911094930877 |
| 17 | 14837831731420 |
| 18 | 256482519928831 |
| 19 | 4689966078698629 |
| 20 | 90449345803473559 |
| 21 | 1834829586299035049 |