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 | 2 |
| 3 | 3 |
| 4 | 9 |
| 5 | 25 |
| 6 | 130 |
| 7 | 721 |
| 8 | 5069 |
| 9 | 40333 |
| 10 | 363006 |
| 11 | 3628801 |
| 12 | 39917607 |
| 13 | 479001601 |
| 14 | 6227025848 |
| 15 | 87178291591 |
| 16 | 1307674408449 |
| 17 | 20922789888001 |
| 18 | 355687428461452 |
| 19 | 6402373705728001 |
| 20 | 121645100412461861 |
| 21 | 2432902008176660217 |
| 22 | 51090942171749356812 |
| 23 | 1124000727777607680001 |