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 | 0 |
| 1 | 1 |
| 2 | 13 |
| 3 | 144 |
| 4 | 1573 |
| 5 | 17161 |
| 6 | 187200 |
| 7 | 2042041 |
| 8 | 22275253 |
| 9 | 242985744 |
| 10 | 2650567933 |
| 11 | 28913261521 |
| 12 | 315395308800 |
| 13 | 3440435135281 |
| 14 | 37529391179293 |
| 15 | 409382867836944 |
| 16 | 4465682155027093 |
| 17 | 48713120837461081 |
| 18 | 531378647057044800 |
| 19 | 5796451996790031721 |
| 20 | 63229593317633304133 |