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 | 5 |
| 4 | 15 |
| 5 | 52 |
| 6 | 203 |
| 7 | 877 |
| 8 | 4140 |
| 9 | 21146 |
| 10 | 115945 |
| 11 | 678012 |
| 12 | 4205209 |
| 13 | 27531954 |
| 14 | 189486817 |
| 15 | 1365888674 |
| 16 | 10278272450 |
| 17 | 80503198320 |
| 18 | 654544093035 |
| 19 | 5511256984436 |
| 20 | 47950929125540 |