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 | 5 |
| 3 | 40 |
| 4 | 405 |
| 5 | 4745 |
| 6 | 61551 |
| 7 | 862050 |
| 8 | 12831835 |
| 9 | 200874055 |
| 10 | 3282575310 |
| 11 | 55693595381 |
| 12 | 977058059380 |
| 13 | 17668078651755 |
| 14 | 328497282637520 |
| 15 | 6267311264123850 |
| 16 | 122498870023756800 |
| 17 | 2449635783413544555 |
| 18 | 50061311067746399725 |
| 19 | 1044531750427750075150 |
| 20 | 22233430278290842445120 |