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 | 0 |
| 2 | 1 |
| 3 | 7 |
| 4 | 59 |
| 5 | 577 |
| 6 | 6435 |
| 7 | 80731 |
| 8 | 1126321 |
| 9 | 17306899 |
| 10 | 290514275 |
| 11 | 5290386805 |
| 12 | 103892269503 |
| 13 | 2188786203451 |
| 14 | 49246871008285 |
| 15 | 1178620260610039 |
| 16 | 29898497436003155 |
| 17 | 801364442718809233 |
| 18 | 22629823094599476315 |
| 19 | 671564575318740405283 |
| 20 | 20894818098241648524577 |
| 21 | 680161672262047334987995 |