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 | 5 |
| 2 | 20 |
| 3 | 70 |
| 4 | 350 |
| 5 | 820 |
| 6 | 8030 |
| 7 | 13170 |
| 8 | 102750 |
| 9 | 327050 |
| 10 | 2444780 |
| 11 | 4884430 |
| 12 | 61632150 |
| 13 | 101732420 |
| 14 | 1017309930 |
| 15 | 3816214730 |
| 16 | 19104506250 |
| 17 | 47683838320 |
| 18 | 635787430450 |
| 19 | 1059638680670 |
| 20 | 11924777944650 |
| 21 | 39736963208630 |