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 | 0 |
| 4 | 0 |
| 5 | 1 |
| 6 | 3 |
| 7 | 23 |
| 8 | 177 |
| 9 | 1553 |
| 10 | 14963 |
| 11 | 157931 |
| 12 | 1814453 |
| 13 | 22566237 |
| 14 | 302267423 |
| 15 | 4340478951 |
| 16 | 66541218865 |
| 17 | 1084982173641 |
| 18 | 18752743351339 |
| 19 | 342523093859011 |
| 20 | 6593167693927885 |
| 21 | 133408305489947029 |
| 22 | 2831112931136162775 |
| 23 | 62878579846490149375 |
| 24 | 1458746608689369440265 |