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 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 1 |
| 5 | 6 |
| 6 | 22 |
| 7 | 64 |
| 8 | 198 |
| 9 | 1138 |
| 10 | 10004 |
| 11 | 83920 |
| 12 | 617993 |
| 13 | 4226028 |
| 14 | 30103686 |
| 15 | 251883012 |
| 16 | 2490287821 |
| 17 | 26456763078 |
| 18 | 281404300348 |
| 19 | 2966101610920 |
| 20 | 31877462564554 |
| 21 | 362624252399566 |
| 22 | 4437794875670072 |
| 23 | 57612897938229380 |
| 24 | 773900876490016325 |
| 25 | 10599854900351622752 |