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 | 0 |
| 1 | 2 |
| 2 | 60 |
| 3 | 660 |
| 4 | 4290 |
| 5 | 20020 |
| 6 | 74256 |
| 7 | 232560 |
| 8 | 639540 |
| 9 | 1586310 |
| 10 | 3617900 |
| 11 | 7696260 |
| 12 | 15438150 |
| 13 | 29451240 |
| 14 | 53796160 |
| 15 | 94607040 |
| 16 | 160908264 |
| 17 | 265670730 |
| 18 | 427156860 |
| 19 | 670609940 |
| 20 | 1030350090 |
| 21 | 1552346268 |
| 22 | 2297341200 |
| 23 | 3344614000 |
| 24 | 4796473500 |