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 | 0 |
| 2 | 1 |
| 3 | 1 |
| 4 | 9 |
| 5 | 51 |
| 6 | 369 |
| 7 | 2661 |
| 8 | 19929 |
| 9 | 151936 |
| 10 | 1178289 |
| 11 | 9259812 |
| 12 | 73593729 |
| 13 | 590475744 |
| 14 | 4776464121 |
| 15 | 38912018796 |
| 16 | 318971849625 |
| 17 | 2629040965776 |
| 18 | 21774894337449 |
| 19 | 181136924953317 |
| 20 | 1512731101731499 |
| 21 | 12678230972826340 |
| 22 | 106600213003114719 |