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) |
|---|---|
| 2 | 1 |
| 3 | 4 |
| 4 | 20 |
| 5 | 138 |
| 6 | 1258 |
| 7 | 14476 |
| 8 | 202655 |
| 9 | 3354848 |
| 10 | 64246776 |
| 11 | 1398909332 |
| 12 | 34157026526 |
| 13 | 924757926320 |
| 14 | 27503093599024 |
| 15 | 891534666547216 |
| 16 | 31289986924954924 |
| 17 | 1182213869836721036 |
| 18 | 47846600590876178320 |
| 19 | 2065282617724684345208 |