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 | 1 |
| 1 | 1 |
| 2 | 0 |
| 3 | 1 |
| 4 | 3 |
| 5 | 13 |
| 6 | 64 |
| 7 | 406 |
| 8 | 2737 |
| 9 | 23044 |
| 10 | 200509 |
| 11 | 2078460 |
| 12 | 22323513 |
| 13 | 275402437 |
| 14 | 3501602483 |
| 15 | 50310672046 |
| 16 | 739235942264 |
| 17 | 12084285146335 |
| 18 | 202054808987101 |
| 19 | 3703410393626031 |
| 20 | 69269248667062892 |
| 21 | 1409725495837854024 |
| 22 | 29169764518508360709 |
| 23 | 651568557906956269430 |