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 | 0 |
| 3 | 3 |
| 4 | 12 |
| 5 | 36 |
| 6 | 99 |
| 7 | 264 |
| 8 | 696 |
| 9 | 1827 |
| 10 | 4788 |
| 11 | 12540 |
| 12 | 32835 |
| 13 | 85968 |
| 14 | 225072 |
| 15 | 589251 |
| 16 | 1542684 |
| 17 | 4038804 |
| 18 | 10573731 |
| 19 | 27682392 |
| 20 | 72473448 |
| 21 | 189737955 |
| 22 | 496740420 |
| 23 | 1300483308 |
| 24 | 3404709507 |
| 25 | 8913645216 |
| 26 | 23336226144 |
| 27 | 61095033219 |
| 28 | 159948873516 |
| 29 | 418751587332 |
| 30 | 1096305888483 |