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 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 2 |
| 4 | 14 |
| 5 | 70 |
| 6 | 306 |
| 7 | 1248 |
| 8 | 4888 |
| 9 | 18666 |
| 10 | 70110 |
| 11 | 260414 |
| 12 | 959882 |
| 13 | 3519232 |
| 14 | 12854064 |
| 15 | 46824210 |
| 16 | 170243566 |
| 17 | 618125238 |
| 18 | 2242100898 |
| 19 | 8126927456 |
| 20 | 29442587720 |
| 21 | 106626616954 |
| 22 | 386046638142 |
| 23 | 1397431266222 |
| 24 | 5057790129274 |
| 25 | 18304064121600 |
| 26 | 66237312391776 |