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 | 5 |
| 4 | 20 |
| 5 | 137 |
| 6 | 1478 |
| 7 | 22925 |
| 8 | 481448 |
| 9 | 13138193 |
| 10 | 451749962 |
| 11 | 19104365333 |
| 12 | 974417603132 |
| 13 | 58981977530777 |
| 14 | 4179837144348686 |
| 15 | 342799255549127837 |
| 16 | 32212592211380729168 |
| 17 | 3438255899105307857441 |
| 18 | 413670348773363088131474 |
| 19 | 55722273751954119897519653 |
| 20 | 8352810415786907670280952420 |