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 | 0 |
| 3 | 2 |
| 4 | 1 |
| 5 | 12 |
| 6 | 14 |
| 7 | 100 |
| 8 | 180 |
| 9 | 990 |
| 10 | 2310 |
| 11 | 10920 |
| 12 | 30030 |
| 13 | 129612 |
| 14 | 396576 |
| 15 | 1620168 |
| 16 | 5318841 |
| 17 | 21029580 |
| 18 | 72364578 |
| 19 | 280735884 |
| 20 | 997356360 |
| 21 | 3828988020 |
| 22 | 13905563100 |
| 23 | 53108050320 |
| 24 | 195875639310 |
| 25 | 746569720572 |
| 26 | 2784329809344 |
| 27 | 10610782107800 |