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 | 3 |
| 3 | 9 |
| 4 | 38 |
| 5 | 190 |
| 6 | 1146 |
| 7 | 8022 |
| 8 | 64200 |
| 9 | 577800 |
| 10 | 5778120 |
| 11 | 63559320 |
| 12 | 762712560 |
| 13 | 9915263280 |
| 14 | 138813690960 |
| 15 | 2082205364400 |
| 16 | 33315285870720 |
| 17 | 566359859802240 |
| 18 | 10194477476803200 |
| 19 | 193695072059260800 |
| 20 | 3873901441188844800 |
| 21 | 81351930264965740800 |
| 22 | 1789742465829286214400 |