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 | 5 |
| 3 | 13 |
| 4 | 52 |
| 5 | 261 |
| 6 | 1666 |
| 7 | 14400 |
| 8 | 159250 |
| 9 | 2308545 |
| 10 | 43718544 |
| 11 | 1079620569 |
| 12 | 34863330980 |
| 13 | 1466458546176 |
| 14 | 80646187346132 |
| 15 | 5787269582487581 |
| 16 | 541901038236234048 |
| 17 | 66279540183479379277 |
| 18 | 10578427028263503488000 |