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) |
|---|---|
| 3 | 0 |
| 4 | 0 |
| 5 | 4 |
| 6 | 16 |
| 7 | 60 |
| 8 | 208 |
| 9 | 726 |
| 10 | 2568 |
| 11 | 9196 |
| 12 | 33286 |
| 13 | 121572 |
| 14 | 447392 |
| 15 | 1657006 |
| 16 | 6170928 |
| 17 | 23091220 |
| 18 | 86767014 |
| 19 | 327235608 |
| 20 | 1238188768 |
| 21 | 4698767638 |