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) |
|---|---|
| 1 | 0 |
| 2 | 2 |
| 3 | 6 |
| 4 | 36 |
| 5 | 260 |
| 6 | 1950 |
| 7 | 19362 |
| 8 | 193256 |
| 9 | 2326536 |
| 10 | 29272410 |
| 11 | 413257790 |
| 12 | 6231230412 |
| 13 | 101415565836 |
| 14 | 1769925341366 |
| 15 | 32734873484250 |
| 16 | 646218442877520 |
| 17 | 13404753632014352 |
| 18 | 294656673023216946 |
| 19 | 6775966692145553526 |