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 | 155 |
| 3 | 1365 |
| 4 | 10990 |
| 5 | 83538 |
| 6 | 610050 |
| 7 | 4325310 |
| 8 | 29979015 |
| 9 | 204086025 |
| 10 | 1369220853 |
| 11 | 9075850875 |
| 12 | 59550467340 |
| 13 | 387359772660 |
| 14 | 2500864350900 |
| 15 | 16040872988748 |
| 16 | 102298452571965 |
| 17 | 649077104453715 |
| 18 | 4099652984281855 |
| 19 | 25788295829930865 |
| 20 | 161619907171129946 |
| 21 | 1009512779437342950 |