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 | 1 |
| 3 | 3 |
| 4 | 24 |
| 5 | 200 |
| 6 | 2070 |
| 7 | 24822 |
| 8 | 340648 |
| 9 | 5257800 |
| 10 | 90174690 |
| 11 | 1701190370 |
| 12 | 35011502460 |
| 13 | 780603478668 |
| 14 | 18742820292742 |
| 15 | 482172697215510 |
| 16 | 13231193297338320 |
| 17 | 385766358723033104 |
| 18 | 11908944548154971946 |
| 19 | 388063941316923002634 |
| 20 | 13310969922203225028580 |