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 | 0 |
| 2 | 0 |
| 3 | 3 |
| 4 | 6 |
| 5 | 60 |
| 6 | 390 |
| 7 | 3255 |
| 8 | 29652 |
| 9 | 300384 |
| 10 | 3337380 |
| 11 | 40382595 |
| 12 | 528644490 |
| 13 | 7445077068 |
| 14 | 112248853626 |
| 15 | 1803999434055 |
| 16 | 30788257006920 |
| 17 | 556112892188640 |
| 18 | 10598857474652712 |
| 19 | 212565974908314339 |
| 20 | 4475073155964510510 |