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 | 2487 |
| 9 | 10240 |
| 10 | 40488 |
| 11 | 158220 |
| 12 | 609078 |
| 13 | 2333520 |
| 14 | 8895204 |
| 15 | 33864364 |
| 16 | 128793627 |
| 17 | 490027200 |
| 18 | 1865625340 |
| 19 | 7110959340 |
| 20 | 27138210888 |
| 21 | 103717720000 |
| 22 | 396965694444 |
| 23 | 1521562700988 |
| 24 | 5840509760582 |
| 25 | 22450188684288 |
| 26 | 86412088367640 |
| 27 | 333035003543900 |
| 28 | 1285108410802038 |
| 29 | 4964755661788560 |
| 30 | 19201631174055992 |