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 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 114 |
| 6 | 600 |
| 7 | 3372 |
| 8 | 19824 |
| 9 | 120426 |
| 10 | 749976 |
| 11 | 4762644 |
| 12 | 30723792 |
| 13 | 200778612 |
| 14 | 1326360048 |
| 15 | 8842981848 |
| 16 | 59425117152 |
| 17 | 402092408346 |
| 18 | 2737156004376 |
| 19 | 18732169337604 |
| 20 | 128806616999184 |
| 21 | 889479590046108 |
| 22 | 6165939982059600 |
| 23 | 42891532191557736 |
| 24 | 299307319060137504 |