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 | 15 |
| 2 | 120 |
| 3 | 680 |
| 4 | 3060 |
| 5 | 11628 |
| 6 | 38760 |
| 7 | 116280 |
| 8 | 316767 |
| 9 | 788161 |
| 10 | 1805100 |
| 11 | 3840420 |
| 12 | 7660250 |
| 13 | 14446134 |
| 14 | 25947612 |
| 15 | 44668692 |
| 16 | 74091645 |
| 17 | 118941555 |
| 18 | 185495056 |
| 19 | 281936688 |
| 20 | 418766304 |
| 21 | 609260960 |
| 22 | 869994720 |
| 23 | 1221419808 |
| 24 | 1688512539 |
| 25 | 2301487461 |
| 26 | 3096583140 |
| 27 | 4116923020 |