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 | 0 |
| 3 | 6 |
| 4 | 28 |
| 5 | 193 |
| 6 | 1140 |
| 7 | 7688 |
| 8 | 52364 |
| 9 | 373560 |
| 10 | 2732836 |
| 11 | 20506254 |
| 12 | 156899748 |
| 13 | 1221179922 |
| 14 | 9642327324 |
| 15 | 77092881840 |
| 16 | 623120435820 |
| 17 | 5085013101160 |
| 18 | 41850590485164 |
| 19 | 347060754685884 |
| 20 | 2897800074184240 |
| 21 | 24344668688255109 |
| 22 | 205667186830447412 |
| 23 | 1746375819789491992 |