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 | 3 |
| 4 | 29 |
| 5 | 198 |
| 6 | 1180 |
| 7 | 6570 |
| 8 | 35196 |
| 9 | 184128 |
| 10 | 948516 |
| 11 | 4835295 |
| 12 | 24469005 |
| 13 | 123174810 |
| 14 | 617662890 |
| 15 | 3088403955 |
| 16 | 15409111025 |
| 17 | 76755126600 |
| 18 | 381848749720 |
| 19 | 1897825700385 |
| 20 | 9425387927295 |
| 21 | 46783757341050 |
| 22 | 232114595171200 |