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 | 4 |
| 4 | 5 |
| 5 | 33 |
| 6 | 91 |
| 7 | 408 |
| 8 | 1485 |
| 9 | 6195 |
| 10 | 24838 |
| 11 | 103752 |
| 12 | 432796 |
| 13 | 1834140 |
| 14 | 7815900 |
| 15 | 33591376 |
| 16 | 145197017 |
| 17 | 631281591 |
| 18 | 2757917260 |
| 19 | 12102728740 |
| 20 | 53321334381 |
| 21 | 235768155073 |
| 22 | 1045889996047 |
| 23 | 4653534540816 |
| 24 | 20761857325000 |
| 25 | 92862669150004 |
| 26 | 416316199107096 |
| 27 | 1870414803490240 |