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 | 315 |
| 5 | 3465 |
| 6 | 45045 |
| 7 | 135135 |
| 8 | 2297295 |
| 9 | 43648605 |
| 10 | 130945815 |
| 11 | 3011753745 |
| 12 | 75293843625 |
| 13 | 225881530875 |
| 14 | 6550564395375 |
| 15 | 203067496256625 |
| 16 | 609202488769875 |
| 17 | 21322087106945625 |
| 18 | 788917222956988125 |