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 | 6 |
| 3 | 24 |
| 4 | 120 |
| 5 | 570 |
| 6 | 2850 |
| 7 | 14100 |
| 8 | 70500 |
| 9 | 351750 |
| 10 | 1758750 |
| 11 | 8790000 |
| 12 | 43950000 |
| 13 | 219731250 |
| 14 | 1098656250 |
| 15 | 5493187500 |
| 16 | 27465937500 |
| 17 | 137329218750 |
| 18 | 686646093750 |
| 19 | 3433228125000 |
| 20 | 17166140625000 |
| 21 | 85830691406250 |
| 22 | 429153457031250 |
| 23 | 2145767226562500 |
| 24 | 10728836132812500 |
| 25 | 53644180371093750 |