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 | 3 |
| 3 | 15 |
| 4 | 82 |
| 5 | 518 |
| 6 | 3652 |
| 7 | 28123 |
| 8 | 233733 |
| 9 | 2075597 |
| 10 | 19542826 |
| 11 | 193908574 |
| 12 | 2017519282 |
| 13 | 21921326573 |
| 14 | 247882099197 |
| 15 | 2908534759303 |
| 16 | 35322473621014 |
| 17 | 443010881207381 |
| 18 | 5726889928765906 |
| 19 | 76175517383629544 |
| 20 | 1040964231177762308 |
| 21 | 14594191539892866665 |