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 | 1 |
| 3 | 4 |
| 4 | 1 |
| 5 | 2 |
| 6 | 61 |
| 7 | 9 |
| 8 | 104 |
| 9 | 2586 |
| 10 | 270 |
| 11 | 5460 |
| 12 | 184710 |
| 13 | 12600 |
| 14 | 458640 |
| 15 | 20113380 |
| 16 | 982800 |
| 17 | 53373600 |
| 18 | 3042295200 |
| 19 | 109544400 |
| 20 | 8497742400 |
| 21 | 611967862800 |
| 22 | 16922228400 |
| 23 | 1762112167200 |
| 24 | 157184659447200 |
| 25 | 3432645216000 |
| 26 | 463679536320000 |
| 27 | 50284574580240000 |
| 28 | 888196949640000 |
| 29 | 150857156385936000 |
| 30 | 19562163412303512000 |