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) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 6 |
| 4 | 45 |
| 5 | 400 |
| 6 | 4115 |
| 7 | 48146 |
| 8 | 631729 |
| 9 | 9189972 |
| 10 | 146829039 |
| 11 | 2556200086 |
| 12 | 48167698733 |
| 13 | 976792093784 |
| 14 | 21211601837803 |
| 15 | 491112582793626 |
| 16 | 12077021182230057 |
| 17 | 314362864408454236 |
| 18 | 8635229233659916007 |
| 19 | 249631741661080132766 |
| 20 | 7575921686807827601701 |
| 21 | 240827454421807200901728 |