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 | 1 |
| 2 | 2 |
| 3 | 3 |
| 4 | 12 |
| 5 | 20 |
| 6 | 72 |
| 7 | 168 |
| 8 | 528 |
| 9 | 1440 |
| 10 | 4480 |
| 11 | 13046 |
| 12 | 40008 |
| 13 | 120055 |
| 14 | 366324 |
| 15 | 1109745 |
| 16 | 3380752 |
| 17 | 10269819 |
| 18 | 31253904 |
| 19 | 95011267 |
| 20 | 288979680 |
| 21 | 878550498 |
| 22 | 2671223720 |
| 23 | 8120041693 |
| 24 | 24682865208 |
| 25 | 75020015675 |
| 26 | 227999634772 |
| 27 | 692872971246 |
| 28 | 2105464666676 |