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 | 2 |
| 3 | 4 |
| 4 | 11 |
| 5 | 50 |
| 6 | 389 |
| 7 | 4590 |
| 8 | 73950 |
| 9 | 1559648 |
| 10 | 41768100 |
| 11 | 1372257648 |
| 12 | 53854228438 |
| 13 | 2482184155472 |
| 14 | 132554850677690 |
| 15 | 8096323604940164 |
| 16 | 559278345518698923 |
| 17 | 43305732768029924394 |
| 18 | 3731115433469990603265 |