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 | 4 |
| 3 | 20 |
| 4 | 128 |
| 5 | 1024 |
| 6 | 9856 |
| 7 | 110720 |
| 8 | 1421312 |
| 9 | 20525056 |
| 10 | 329334784 |
| 11 | 5812797440 |
| 12 | 111923560448 |
| 13 | 2334639652864 |
| 14 | 52444850814976 |
| 15 | 1262260748288000 |
| 16 | 32405895451246592 |
| 17 | 883950436237705216 |
| 18 | 25530268718794276864 |