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 | 3 |
| 3 | 13 |
| 4 | 61 |
| 5 | 421 |
| 6 | 2641 |
| 7 | 23521 |
| 8 | 203281 |
| 9 | 2071441 |
| 10 | 22407841 |
| 11 | 286403041 |
| 12 | 3453468481 |
| 13 | 51122111041 |
| 14 | 759194916481 |
| 15 | 12216117513601 |
| 16 | 203300293996801 |
| 17 | 3811792426041601 |
| 18 | 69634723878720001 |
| 19 | 1444704854104512001 |
| 20 | 29725332567567436801 |
| 21 | 658231789483184716801 |