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 | 1 |
| 3 | 4 |
| 4 | 27 |
| 5 | 248 |
| 6 | 2830 |
| 7 | 38232 |
| 8 | 593859 |
| 9 | 10401712 |
| 10 | 202601898 |
| 11 | 4342263000 |
| 12 | 101551822350 |
| 13 | 2573779506192 |
| 14 | 70282204726396 |
| 15 | 2057490936366320 |
| 16 | 64291032462761955 |
| 17 | 2136017303903513184 |
| 18 | 75197869250518812754 |
| 19 | 2796475872605709079512 |
| 20 | 109549714522464120960474 |
| 21 | 4509302910783496963256400 |
| 22 | 194584224274515194731540740 |