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 | 2 |
| 3 | 6 |
| 4 | 23 |
| 5 | 110 |
| 6 | 630 |
| 7 | 4210 |
| 8 | 32150 |
| 9 | 276210 |
| 10 | 2636720 |
| 11 | 27687440 |
| 12 | 317169270 |
| 13 | 3936056080 |
| 14 | 52603684760 |
| 15 | 753241509900 |
| 16 | 11504852242400 |
| 17 | 186705357825800 |
| 18 | 3208160592252000 |
| 19 | 58188413286031600 |
| 20 | 1110946958902609400 |