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 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 9 |
| 4 | 52 |
| 5 | 375 |
| 6 | 3246 |
| 7 | 32781 |
| 8 | 378344 |
| 9 | 4912515 |
| 10 | 70872610 |
| 11 | 1124723193 |
| 12 | 19471590876 |
| 13 | 365190378735 |
| 14 | 7376016877334 |
| 15 | 159620144556645 |
| 16 | 3684531055645648 |
| 17 | 90366129593683035 |
| 18 | 2346673806524446218 |
| 19 | 64325158601880061137 |
| 20 | 1856031746386568222660 |
| 21 | 56231443721132068265415 |