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 | 3 |
| 2 | 15 |
| 3 | 90 |
| 4 | 633 |
| 5 | 5028 |
| 6 | 44217 |
| 7 | 424434 |
| 8 | 4399953 |
| 9 | 48858984 |
| 10 | 577372809 |
| 11 | 7221983838 |
| 12 | 95192539641 |
| 13 | 1317190650636 |
| 14 | 19071213218745 |
| 15 | 288112248054882 |
| 16 | 4530217559806497 |
| 17 | 73976635012027344 |
| 18 | 1252091246140278153 |
| 19 | 21926952634345281030 |
| 20 | 396671314081806278601 |