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 | 6 |
| 4 | 61 |
| 5 | 770 |
| 6 | 12160 |
| 7 | 228382 |
| 8 | 4989621 |
| 9 | 124262532 |
| 10 | 3475892685 |
| 11 | 107901412520 |
| 12 | 3681266754660 |
| 13 | 136918473752216 |
| 14 | 5513911474915116 |
| 15 | 239034083286873630 |
| 16 | 11098790133822288645 |
| 17 | 549539910028075555016 |
| 18 | 28903562131933534643851 |
| 19 | 1609321474965547356327246 |