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 | 26 |
| 4 | 224 |
| 5 | 2337 |
| 6 | 28088 |
| 7 | 377144 |
| 8 | 5544824 |
| 9 | 88039724 |
| 10 | 1494960308 |
| 11 | 26954440490 |
| 12 | 513267546824 |
| 13 | 10279486681982 |
| 14 | 215822203235952 |
| 15 | 4737785187211908 |
| 16 | 108509135362455192 |
| 17 | 2588049036893027820 |
| 18 | 64180886929824389840 |
| 19 | 1652564046132761428040 |
| 20 | 44124859215715377422552 |
| 21 | 1220338620776444854394561 |