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 | 3 |
| 2 | 6 |
| 3 | 66 |
| 4 | 210 |
| 5 | 3570 |
| 6 | 207690 |
| 7 | 930930 |
| 8 | 56812470 |
| 9 | 1803571770 |
| 10 | 32395433070 |
| 11 | 265257422430 |
| 12 | 91348974206490 |
| 13 | 24630635909489610 |
| 14 | 438603767516904990 |
| 15 | 14193386885746698630 |
| 16 | 2378522762792139793830 |
| 17 | 351206814022419685159830 |
| 18 | 28791787439593010836313310 |