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 | 2 |
| 3 | 6 |
| 4 | 20 |
| 5 | 96 |
| 6 | 582 |
| 7 | 4672 |
| 8 | 47330 |
| 9 | 595680 |
| 10 | 9088942 |
| 11 | 164702708 |
| 12 | 3483060060 |
| 13 | 84705352206 |
| 14 | 2339732572312 |
| 15 | 72635597193630 |
| 16 | 2511496037777828 |
| 17 | 95965484116697442 |
| 18 | 4024669707807276532 |
| 19 | 184149183428282681030 |
| 20 | 9143767110701151656280 |