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) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 18 |
| 4 | 502 |
| 5 | 9721 |
| 6 | 135902 |
| 7 | 1430707 |
| 8 | 11752870 |
| 9 | 78770466 |
| 10 | 442714845 |
| 11 | 2151608163 |
| 12 | 9202214058 |
| 13 | 35373572486 |
| 14 | 123540794708 |
| 15 | 398005342048 |
| 16 | 1190430659772 |
| 17 | 3344070542314 |
| 18 | 8854626554163 |
| 19 | 22304900540858 |
| 20 | 53543330420874 |