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 | 12 |
| 2 | 100 |
| 3 | 700 |
| 4 | 4410 |
| 5 | 25872 |
| 6 | 144144 |
| 7 | 772200 |
| 8 | 4011150 |
| 9 | 20323160 |
| 10 | 100876776 |
| 11 | 492156392 |
| 12 | 2366136500 |
| 13 | 11232648000 |
| 14 | 52739956800 |
| 15 | 245240799120 |
| 16 | 1130632213590 |
| 17 | 5172827121000 |
| 18 | 23504600427000 |
| 19 | 106141827191400 |
| 20 | 476627347816620 |
| 21 | 2129348151284640 |
| 22 | 9468445336740000 |