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 | 0 |
| 1 | 0 |
| 2 | 3 |
| 3 | 17 |
| 4 | 66 |
| 5 | 222 |
| 6 | 701 |
| 7 | 2151 |
| 8 | 6516 |
| 9 | 19628 |
| 10 | 58983 |
| 11 | 177069 |
| 12 | 531350 |
| 13 | 1594218 |
| 14 | 4782849 |
| 15 | 14348771 |
| 16 | 43046568 |
| 17 | 129139992 |
| 18 | 387420299 |
| 19 | 1162261257 |
| 20 | 3486784170 |
| 21 | 10460352950 |
| 22 | 31381059333 |
| 23 | 94143178527 |
| 24 | 282429536156 |
| 25 | 847288609092 |
| 26 | 2541865827951 |
| 27 | 7625597484581 |
| 28 | 22876792454526 |