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 | 0 |
| 2 | 1 |
| 3 | 1 |
| 4 | 4 |
| 5 | 10 |
| 6 | 30 |
| 7 | 106 |
| 8 | 316 |
| 9 | 1254 |
| 10 | 4140 |
| 11 | 17128 |
| 12 | 63856 |
| 13 | 271492 |
| 14 | 1126216 |
| 15 | 4936608 |
| 16 | 22278712 |
| 17 | 101330506 |
| 18 | 487735440 |
| 19 | 2313734596 |
| 20 | 11706759352 |
| 21 | 58073844300 |
| 22 | 305941244576 |
| 23 | 1587272257096 |
| 24 | 8656011151184 |
| 25 | 46886237603400 |
| 26 | 263791190603200 |
| 27 | 1487539434072976 |