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 | 0 |
| 1 | 1 |
| 2 | 3 |
| 3 | 8 |
| 4 | 28 |
| 5 | 124 |
| 6 | 732 |
| 7 | 5046 |
| 8 | 40352 |
| 9 | 362898 |
| 10 | 3628932 |
| 11 | 39916810 |
| 12 | 479002388 |
| 13 | 6227020812 |
| 14 | 87178296258 |
| 15 | 1307674368272 |
| 16 | 20922789928384 |
| 17 | 355687428096016 |
| 18 | 6402373706092350 |
| 19 | 121645100408832018 |
| 20 | 2432902008180269152 |
| 21 | 51090942171709450128 |
| 22 | 1124000727777647596830 |