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 | 3 |
| 1 | 6 |
| 2 | 28 |
| 3 | 165 |
| 4 | 1092 |
| 5 | 7752 |
| 6 | 57684 |
| 7 | 444015 |
| 8 | 3506100 |
| 9 | 28242984 |
| 10 | 231180144 |
| 11 | 1917334783 |
| 12 | 16077354108 |
| 13 | 136074334200 |
| 14 | 1160946392760 |
| 15 | 9973891723635 |
| 16 | 86210635955220 |
| 17 | 749191930237608 |
| 18 | 6541908910355280 |
| 19 | 57369142749576660 |
| 20 | 505045163173167760 |
| 21 | 4461713825057817120 |