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 | 3 |
| 3 | 12 |
| 4 | 30 |
| 5 | 120 |
| 6 | 315 |
| 7 | 1344 |
| 8 | 3780 |
| 9 | 17280 |
| 10 | 51975 |
| 11 | 253440 |
| 12 | 810810 |
| 13 | 4193280 |
| 14 | 14189175 |
| 15 | 77414400 |
| 16 | 275675400 |
| 17 | 1579253760 |
| 18 | 5892561675 |
| 19 | 35300966400 |
| 20 | 137493105750 |
| 21 | 858370867200 |
| 22 | 3478575575475 |
| 23 | 22562891366400 |
| 24 | 94870242967500 |
| 25 | 637646929920000 |
| 26 | 2774954606799375 |