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 | 4 |
| 2 | 14 |
| 3 | 48 |
| 4 | 168 |
| 5 | 624 |
| 6 | 2592 |
| 7 | 12816 |
| 8 | 78768 |
| 9 | 599184 |
| 10 | 5426352 |
| 11 | 56195856 |
| 12 | 647589168 |
| 13 | 8169788304 |
| 14 | 111687656112 |
| 15 | 1642737336336 |
| 16 | 25851001897008 |
| 17 | 433240433787024 |
| 18 | 7702095007089072 |
| 19 | 144751385430099216 |
| 20 | 2867156164466937648 |
| 21 | 59692410665110252944 |