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 | 2 |
| 2 | 6 |
| 3 | 24 |
| 4 | 66 |
| 5 | 180 |
| 6 | 496 |
| 7 | 1272 |
| 8 | 3202 |
| 9 | 7798 |
| 10 | 18980 |
| 11 | 45076 |
| 12 | 106288 |
| 13 | 246956 |
| 14 | 568776 |
| 15 | 1299184 |
| 16 | 2944654 |
| 17 | 6630660 |
| 18 | 14838606 |
| 19 | 33026000 |
| 20 | 73126376 |
| 21 | 161198136 |
| 22 | 353812612 |
| 23 | 773645124 |
| 24 | 1685548792 |
| 25 | 3660364490 |
| 26 | 7924414752 |
| 27 | 17107225340 |
| 28 | 36832846344 |
| 29 | 79107019964 |
| 30 | 169505684844 |