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 | 3 |
| 3 | 13 |
| 4 | 62 |
| 5 | 352 |
| 6 | 2348 |
| 7 | 17880 |
| 8 | 153138 |
| 9 | 1458726 |
| 10 | 15303672 |
| 11 | 175387056 |
| 12 | 2180632824 |
| 13 | 29240091480 |
| 14 | 420683340840 |
| 15 | 6464876260440 |
| 16 | 105699125013120 |
| 17 | 1832140771795440 |
| 18 | 33562515077608320 |
| 19 | 647929998101403360 |
| 20 | 13148236101412979280 |
| 21 | 279809650659550924080 |