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 | 1 |
| 2 | 6 |
| 3 | 20 |
| 4 | 56 |
| 5 | 160 |
| 6 | 480 |
| 7 | 1456 |
| 8 | 4384 |
| 9 | 13136 |
| 10 | 39360 |
| 11 | 118064 |
| 12 | 354272 |
| 13 | 1062928 |
| 14 | 3188736 |
| 15 | 9565936 |
| 16 | 28697632 |
| 17 | 86093264 |
| 18 | 258280512 |
| 19 | 774841520 |
| 20 | 2324523104 |
| 21 | 6973567888 |
| 22 | 20920705152 |
| 23 | 62762119792 |
| 24 | 188286360736 |
| 25 | 564859074896 |
| 26 | 1694577214656 |
| 27 | 5083731648560 |