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 | 2 |
| 2 | 1 |
| 3 | 4 |
| 4 | 15 |
| 5 | 66 |
| 6 | 291 |
| 7 | 1368 |
| 8 | 6555 |
| 9 | 32262 |
| 10 | 161505 |
| 11 | 821280 |
| 12 | 4227710 |
| 13 | 21996052 |
| 14 | 115469442 |
| 15 | 610894004 |
| 16 | 3253836785 |
| 17 | 17434360442 |
| 18 | 93907348819 |
| 19 | 508194420136 |
| 20 | 2761768079091 |
| 21 | 15065823780102 |
| 22 | 82469439357341 |