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 | 101 |
| 6 | 606 |
| 7 | 4241 |
| 8 | 33928 |
| 9 | 305353 |
| 10 | 3053530 |
| 11 | 33588829 |
| 12 | 403065948 |
| 13 | 5239857325 |
| 14 | 73358002550 |
| 15 | 1100370038249 |
| 16 | 17605920611984 |
| 17 | 299300650403729 |
| 18 | 5387411707267122 |
| 19 | 102360822438075317 |
| 20 | 2047216448761506340 |