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 | 1 |
| 2 | 2 |
| 3 | 3 |
| 4 | 5 |
| 5 | 11 |
| 6 | 23 |
| 7 | 63 |
| 8 | 153 |
| 9 | 489 |
| 10 | 1329 |
| 11 | 4785 |
| 12 | 14235 |
| 13 | 56475 |
| 14 | 181215 |
| 15 | 780255 |
| 16 | 2672145 |
| 17 | 12348945 |
| 18 | 44781345 |
| 19 | 220253985 |
| 20 | 840523635 |
| 21 | 4370620275 |
| 22 | 17465201775 |
| 23 | 95498916975 |
| 24 | 397983749625 |
| 25 | 2278224696825 |
| 26 | 9867844134225 |
| 27 | 58917607974225 |