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 | 3 |
| 3 | 7 |
| 4 | 29 |
| 5 | 121 |
| 6 | 745 |
| 7 | 5041 |
| 8 | 40425 |
| 9 | 362917 |
| 10 | 3629411 |
| 11 | 39916801 |
| 12 | 479006233 |
| 13 | 6227020801 |
| 14 | 87178326495 |
| 15 | 1307674369891 |
| 16 | 20922790211057 |
| 17 | 355687428096001 |
| 18 | 6402373709009185 |
| 19 | 121645100408832001 |
| 20 | 2432902008212933061 |
| 21 | 51090942171709581289 |
| 22 | 1124000727778046764823 |