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 | 2 |
| 6 | 7 |
| 7 | 51 |
| 8 | 300 |
| 9 | 2238 |
| 10 | 18028 |
| 11 | 164945 |
| 12 | 1662067 |
| 13 | 18423138 |
| 14 | 222380433 |
| 15 | 2905942904 |
| 16 | 40864642560 |
| 17 | 615376173176 |
| 18 | 9880203467184 |
| 19 | 168483518571789 |
| 20 | 3041127459127222 |
| 21 | 57926238289894992 |
| 22 | 1161157775616335125 |
| 23 | 24434798429947993043 |
| 24 | 538583682037962702384 |