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 | 3 |
| 2 | 15 |
| 3 | 105 |
| 4 | 945 |
| 5 | 10395 |
| 6 | 135135 |
| 7 | 2297295 |
| 8 | 43648605 |
| 9 | 1003917915 |
| 10 | 25097947875 |
| 11 | 727840488375 |
| 12 | 22563055139625 |
| 13 | 834833040166125 |
| 14 | 34228154646811125 |
| 15 | 1471810649812878375 |
| 16 | 69175100541205283625 |
| 17 | 3389579926519058897625 |
| 18 | 179647736105510121574125 |
| 19 | 10599216430225097172873375 |
| 20 | 646552202243730927545275875 |