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 | 1 |
| 1 | 0 |
| 2 | 3 |
| 3 | 0 |
| 4 | 15 |
| 5 | 12 |
| 6 | 99 |
| 7 | 168 |
| 8 | 759 |
| 9 | 1764 |
| 10 | 6315 |
| 11 | 16896 |
| 12 | 54783 |
| 13 | 156156 |
| 14 | 484851 |
| 15 | 1421784 |
| 16 | 4330887 |
| 17 | 12861588 |
| 18 | 38846907 |
| 19 | 116016432 |
| 20 | 349097871 |
| 21 | 1045196460 |
| 22 | 3139783683 |
| 23 | 9410962440 |
| 24 | 28249664535 |
| 25 | 84715439172 |
| 26 | 254213426379 |
| 27 | 762506061408 |