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 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 12 |
| 5 | 36 |
| 6 | 120 |
| 7 | 408 |
| 8 | 1440 |
| 9 | 5160 |
| 10 | 18816 |
| 11 | 69336 |
| 12 | 258048 |
| 13 | 967344 |
| 14 | 3649536 |
| 15 | 13839504 |
| 16 | 52715952 |
| 17 | 201556944 |
| 18 | 773182608 |
| 19 | 2974442112 |
| 20 | 11471570352 |
| 21 | 44341125312 |
| 22 | 171732665520 |
| 23 | 666302137056 |
| 24 | 2589317125824 |
| 25 | 10076939895984 |
| 26 | 39268487472336 |
| 27 | 153208051192848 |