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 | 15 |
| 2 | 4163 |
| 3 | 158364 |
| 4 | 3904260 |
| 5 | 60560175 |
| 6 | 671224467 |
| 7 | 5697401802 |
| 8 | 38983643908 |
| 9 | 223245029176 |
| 10 | 1100925116264 |
| 11 | 4780871048064 |
| 12 | 18612106195456 |
| 13 | 65909241461760 |
| 14 | 214868401724416 |
| 15 | 650515953570304 |
| 16 | 1842743223078144 |
| 17 | 4916155345428736 |
| 18 | 12422627638293760 |
| 19 | 29881211844270336 |
| 20 | 68721268507385344 |
| 21 | 151698799246127104 |