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 | 6 |
| 4 | 40 |
| 5 | 186 |
| 6 | 816 |
| 7 | 3396 |
| 8 | 14040 |
| 9 | 57306 |
| 10 | 233000 |
| 11 | 943608 |
| 12 | 3813000 |
| 13 | 15378716 |
| 14 | 61946640 |
| 15 | 249260316 |
| 16 | 1002158880 |
| 17 | 4026527706 |
| 18 | 16169288640 |
| 19 | 64901712996 |
| 20 | 260410648680 |
| 21 | 1044535993800 |
| 22 | 4188615723280 |
| 23 | 16792541033556 |
| 24 | 67309233561240 |
| 25 | 269746851976156 |