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 | 36 |
| 3 | 252 |
| 4 | 1548 |
| 5 | 9324 |
| 6 | 55980 |
| 7 | 335916 |
| 8 | 2015532 |
| 9 | 12093228 |
| 10 | 72559404 |
| 11 | 435356460 |
| 12 | 2612138796 |
| 13 | 15672832812 |
| 14 | 94036996908 |
| 15 | 564221981484 |
| 16 | 3385331888940 |
| 17 | 20311991333676 |
| 18 | 121871948002092 |
| 19 | 731231688012588 |
| 20 | 4387390128075564 |
| 21 | 26324340768453420 |