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 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 7 |
| 5 | 40 |
| 6 | 355 |
| 7 | 4720 |
| 8 | 91690 |
| 9 | 2559980 |
| 10 | 101724390 |
| 11 | 5724370860 |
| 12 | 455400049575 |
| 13 | 51225573119870 |
| 14 | 8155535394029685 |
| 15 | 1840116104410154380 |
| 16 | 589128078915179209630 |
| 17 | 267942956094193363173030 |
| 18 | 173296035183231212307098790 |
| 19 | 159532934947213401229226873410 |