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) |
|---|---|
| 1 | 0 |
| 2 | 9 |
| 3 | 18 |
| 4 | 108 |
| 5 | 279 |
| 6 | 1260 |
| 7 | 3780 |
| 8 | 15129 |
| 9 | 49158 |
| 10 | 185328 |
| 11 | 627759 |
| 12 | 2295720 |
| 13 | 7945560 |
| 14 | 28607049 |
| 15 | 100117098 |
| 16 | 357580548 |
| 17 | 1258634439 |
| 18 | 4476859380 |
| 19 | 15804569340 |
| 20 | 56096303769 |
| 21 | 198337427838 |
| 22 | 703204161768 |
| 23 | 2488241012319 |
| 24 | 8817078468240 |
| 25 | 31211247579120 |
| 26 | 110564953793289 |