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 | 1 |
| 3 | 2 |
| 4 | 6 |
| 5 | 26 |
| 6 | 152 |
| 7 | 1144 |
| 8 | 10742 |
| 9 | 122772 |
| 10 | 1673856 |
| 11 | 26780972 |
| 12 | 496090330 |
| 13 | 10519217930 |
| 14 | 252851833482 |
| 15 | 6832018188414 |
| 16 | 205985750827854 |
| 17 | 6885220780488694 |
| 18 | 253685194149119818 |
| 19 | 10250343686634687424 |
| 20 | 452108221967363310278 |
| 21 | 21676762640915055856716 |