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 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 30 |
| 5 | 21 |
| 6 | 132 |
| 7 | 3003 |
| 8 | 51051 |
| 9 | 285285 |
| 10 | 13399386 |
| 11 | 1983580599 |
| 12 | 308476470621 |
| 13 | 4664762967711 |
| 14 | 48285399661224 |
| 15 | 1815318072406212 |
| 16 | 99924007282353507 |
| 17 | 3738372398312278947 |
| 18 | 442424606197031564007 |
| 19 | 42728372978287991878884 |