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 | 0 |
| 4 | 3 |
| 5 | 24 |
| 6 | 124 |
| 7 | 588 |
| 8 | 2484 |
| 9 | 10240 |
| 10 | 40464 |
| 11 | 158220 |
| 12 | 608951 |
| 13 | 2333520 |
| 14 | 8894616 |
| 15 | 33864340 |
| 16 | 128791140 |
| 17 | 490027200 |
| 18 | 1865614976 |
| 19 | 7110959340 |
| 20 | 27138170397 |
| 21 | 103717719412 |
| 22 | 396965536224 |
| 23 | 1521562700988 |
| 24 | 5840509149020 |
| 25 | 22450188684264 |
| 26 | 86412086034120 |
| 27 | 333035003533660 |