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 | 210 |
| 6 | 2730 |
| 7 | 30030 |
| 8 | 510510 |
| 9 | 9699690 |
| 10 | 223092870 |
| 11 | 8254436190 |
| 12 | 602573841870 |
| 13 | 17474641414230 |
| 14 | 541713883841130 |
| 15 | 23293697005168590 |
| 16 | 1840202063408318610 |
| 17 | 97530709360640886330 |
| 18 | 8095048876933193565390 |
| 19 | 542368274754523968881130 |
| 20 | 22237099264935482724126330 |