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 | 6 |
| 4 | 24 |
| 5 | 119 |
| 6 | 708 |
| 7 | 4915 |
| 8 | 38992 |
| 9 | 347980 |
| 10 | 3450572 |
| 11 | 37637545 |
| 12 | 447857256 |
| 13 | 5773243451 |
| 14 | 80146549212 |
| 15 | 1192100892680 |
| 16 | 18913413488544 |
| 17 | 318827489139059 |
| 18 | 5690693361661052 |
| 19 | 107215038571876213 |
| 20 | 2126290615269312536 |
| 21 | 44277066284532913066 |
| 22 | 965913951460006237612 |