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 | 2 |
| 1 | 21 |
| 2 | 180 |
| 3 | 1430 |
| 4 | 10920 |
| 5 | 81396 |
| 6 | 596904 |
| 7 | 4326300 |
| 8 | 31081050 |
| 9 | 221760825 |
| 10 | 1573537680 |
| 11 | 11114897976 |
| 12 | 78215948720 |
| 13 | 548652722520 |
| 14 | 3838040704080 |
| 15 | 26784871943928 |
| 16 | 186537501038070 |
| 17 | 1296717366119175 |
| 18 | 8999440181955300 |
| 19 | 62366467037593950 |
| 20 | 431633967218324640 |
| 21 | 2983755440056831440 |
| 22 | 20603495011611002400 |
| 23 | 142131208489591604400 |