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 | 4 |
| 3 | 25 |
| 4 | 218 |
| 5 | 2451 |
| 6 | 33952 |
| 7 | 560407 |
| 8 | 10750140 |
| 9 | 235118665 |
| 10 | 5775676496 |
| 11 | 157448312649 |
| 12 | 4716609543736 |
| 13 | 154007821275595 |
| 14 | 5443783515005760 |
| 15 | 207093963680817511 |
| 16 | 8436365861409555728 |
| 17 | 366403740283162634193 |
| 18 | 16900793597898691865920 |
| 19 | 825115046704241167668025 |