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 | 2 |
| 2 | 6 |
| 3 | 15 |
| 4 | 40 |
| 5 | 145 |
| 6 | 756 |
| 7 | 5089 |
| 8 | 40384 |
| 9 | 362961 |
| 10 | 3628900 |
| 11 | 39916921 |
| 12 | 479001744 |
| 13 | 6227020969 |
| 14 | 87178291396 |
| 15 | 1307674368225 |
| 16 | 20922789888256 |
| 17 | 355687428096289 |
| 18 | 6402373705728324 |
| 19 | 121645100408832361 |
| 20 | 2432902008176640400 |
| 21 | 51090942171709440441 |
| 22 | 1124000727777607680484 |