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 | 20 |
| 2 | 400 |
| 3 | 1260 |
| 4 | 8643 |
| 5 | 32860 |
| 6 | 92560 |
| 7 | 393049 |
| 8 | 1578401 |
| 9 | 5340405 |
| 10 | 20121640 |
| 11 | 78251775 |
| 12 | 284274270 |
| 13 | 1051011118 |
| 14 | 3983096719 |
| 15 | 14785680541 |
| 16 | 54778074707 |
| 17 | 205202336088 |
| 18 | 765281117395 |
| 19 | 2844826058100 |
| 20 | 10615121655468 |
| 21 | 39598654722769 |