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 | 1 |
| 4 | 3 |
| 5 | 15 |
| 6 | 80 |
| 7 | 20 |
| 8 | 160 |
| 9 | 1440 |
| 10 | 75 |
| 11 | 825 |
| 12 | 9900 |
| 13 | 128700 |
| 14 | 165888 |
| 15 | 2488320 |
| 16 | 39813120 |
| 17 | 597196800 |
| 18 | 10749542400 |
| 19 | 125411328000 |
| 20 | 2508226560000 |
| 21 | 52672757760000 |
| 22 | 2769091920000 |
| 23 | 4901791334400 |
| 24 | 117642992025600 |
| 25 | 2941074800640000 |
| 26 | 76467944816640000 |
| 27 | 2064634510049280000 |
| 28 | 57809766281379840000 |
| 29 | 1676483222160015360000 |