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 | 1 |
| 3 | 3 |
| 4 | 12 |
| 5 | 36 |
| 6 | 126 |
| 7 | 1386 |
| 8 | 10248 |
| 9 | 92232 |
| 10 | 805896 |
| 11 | 9862776 |
| 12 | 107908416 |
| 13 | 1428755328 |
| 14 | 17338793472 |
| 15 | 184781653056 |
| 16 | 2707269941376 |
| 17 | 58956779097216 |
| 18 | 931404051946368 |
| 19 | 18440063711701632 |
| 20 | 369535355215842816 |
| 21 | 8290691125502962176 |
| 22 | 161390500012170164736 |