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 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 9 |
| 5 | 23 |
| 6 | 63 |
| 7 | 178 |
| 8 | 514 |
| 9 | 1515 |
| 10 | 4545 |
| 11 | 13827 |
| 12 | 42540 |
| 13 | 132124 |
| 14 | 413741 |
| 15 | 1304891 |
| 16 | 4141198 |
| 17 | 13214815 |
| 18 | 42375461 |
| 19 | 136478383 |
| 20 | 441285890 |
| 21 | 1431925180 |
| 22 | 4661485203 |
| 23 | 15219836738 |
| 24 | 49827678840 |
| 25 | 163535624722 |
| 26 | 537962562453 |
| 27 | 1773437280323 |