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 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 2 |
| 5 | 8 |
| 6 | 43 |
| 7 | 267 |
| 8 | 1927 |
| 9 | 15845 |
| 10 | 146123 |
| 11 | 1493701 |
| 12 | 16762640 |
| 13 | 204876709 |
| 14 | 2708925368 |
| 15 | 38526938568 |
| 16 | 586465620430 |
| 17 | 9513775620310 |
| 18 | 163848357905336 |
| 19 | 2985681188497227 |
| 20 | 57391427290002261 |
| 21 | 1160582196308934615 |