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 | 4 |
| 2 | 28 |
| 3 | 264 |
| 4 | 2860 |
| 5 | 33592 |
| 6 | 416024 |
| 7 | 5348880 |
| 8 | 70715340 |
| 9 | 955277400 |
| 10 | 13128240840 |
| 11 | 182965127280 |
| 12 | 2579808294648 |
| 13 | 36734706144304 |
| 14 | 527495903500720 |
| 15 | 7629973004184608 |
| 16 | 111068129754096396 |
| 17 | 1625888084299461528 |
| 18 | 23919596771720906984 |
| 19 | 353467725574013402800 |