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 | 0 |
| 3 | 1 |
| 4 | 3 |
| 5 | 19 |
| 6 | 135 |
| 7 | 1204 |
| 8 | 12537 |
| 9 | 150556 |
| 10 | 2043930 |
| 11 | 30969211 |
| 12 | 517973148 |
| 13 | 9478800604 |
| 14 | 188381470095 |
| 15 | 4040440921699 |
| 16 | 93020386382742 |
| 17 | 2287969523647171 |
| 18 | 59877222907995675 |
| 19 | 1661259526266784171 |
| 20 | 48705364034046758493 |
| 21 | 1504614657169716311674 |
| 22 | 48848750173492332588525 |