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 | 0 |
| 2 | 2 |
| 3 | 4 |
| 4 | 16 |
| 5 | 56 |
| 6 | 216 |
| 7 | 848 |
| 8 | 3424 |
| 9 | 14080 |
| 10 | 58816 |
| 11 | 248832 |
| 12 | 1064064 |
| 13 | 4591744 |
| 14 | 19970432 |
| 15 | 87448832 |
| 16 | 385226240 |
| 17 | 1705979904 |
| 18 | 7590632448 |
| 19 | 33916934144 |
| 20 | 152128126976 |
| 21 | 684702330880 |
| 22 | 3091429158912 |
| 23 | 13997970530304 |
| 24 | 63550155145216 |
| 25 | 289216809762816 |
| 26 | 1319185060069376 |
| 27 | 6029646893252608 |