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 | 1 |
| 2 | 6 |
| 3 | 56 |
| 4 | 616 |
| 5 | 7392 |
| 6 | 93632 |
| 7 | 1230592 |
| 8 | 16612992 |
| 9 | 228890112 |
| 10 | 3204461568 |
| 11 | 45445091328 |
| 12 | 651379642368 |
| 13 | 9419951751168 |
| 14 | 137262154088448 |
| 15 | 2013178259963904 |
| 16 | 29694379334467584 |
| 17 | 440175505428578304 |
| 18 | 6553724191936610304 |
| 19 | 97960930026841964544 |
| 20 | 1469413950402629468160 |