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 | 0 |
| 2 | 0 |
| 3 | 4 |
| 4 | 0 |
| 5 | 41 |
| 6 | 372 |
| 7 | 3189 |
| 8 | 15544 |
| 9 | 94844 |
| 10 | 606556 |
| 11 | 3341926 |
| 12 | 18243164 |
| 13 | 100641235 |
| 14 | 541792652 |
| 15 | 2853058729 |
| 16 | 14909615644 |
| 17 | 77215251362 |
| 18 | 395393899688 |
| 19 | 2007472847598 |
| 20 | 10120652405244 |
| 21 | 50668068245114 |
| 22 | 252048156500636 |
| 23 | 1246766824001246 |
| 24 | 6135236528242698 |
| 25 | 30045694433419662 |