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 | 1 |
| 3 | 6 |
| 4 | 21 |
| 5 | 112 |
| 6 | 717 |
| 7 | 4592 |
| 8 | 38857 |
| 9 | 318208 |
| 10 | 3158329 |
| 11 | 32169984 |
| 12 | 363525789 |
| 13 | 4399544320 |
| 14 | 56250039237 |
| 15 | 779244812288 |
| 16 | 11210469917713 |
| 17 | 173483433263104 |
| 18 | 2783865475754737 |
| 19 | 47421793222656000 |
| 20 | 840008000833503141 |