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 | 0 |
| 2 | 1 |
| 3 | 5 |
| 4 | 49 |
| 5 | 759 |
| 6 | 16081 |
| 7 | 435833 |
| 8 | 14517441 |
| 9 | 579937319 |
| 10 | 27203499361 |
| 11 | 1474723875789 |
| 12 | 91200920752129 |
| 13 | 6365087902895747 |
| 14 | 496792437580978449 |
| 15 | 43025414912824996889 |
| 16 | 4106965602739453756801 |
| 17 | 429531453143336097416367 |
| 18 | 48964278165034713331278529 |
| 19 | 6055596695306076807138311717 |
| 20 | 809134978410285605488807023681 |