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 | 0 |
| 3 | 0 |
| 4 | 9 |
| 5 | 0 |
| 6 | 24 |
| 7 | 36 |
| 8 | 90 |
| 9 | 228 |
| 10 | 468 |
| 11 | 1296 |
| 12 | 2946 |
| 13 | 7272 |
| 14 | 20808 |
| 15 | 48612 |
| 16 | 143028 |
| 17 | 362700 |
| 18 | 977562 |
| 19 | 2702592 |
| 20 | 7084962 |
| 21 | 20179368 |
| 22 | 54981234 |
| 23 | 154896552 |
| 24 | 438387402 |
| 25 | 1224515736 |
| 26 | 3507218586 |
| 27 | 9902866092 |
| 28 | 28373581638 |
| 29 | 81503463852 |