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 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 0 |
| 6 | 1 |
| 7 | 4 |
| 8 | 13 |
| 9 | 45 |
| 10 | 143 |
| 11 | 461 |
| 12 | 1470 |
| 13 | 4747 |
| 14 | 15364 |
| 15 | 50283 |
| 16 | 165549 |
| 17 | 549734 |
| 18 | 1837539 |
| 19 | 6184589 |
| 20 | 20938983 |
| 21 | 71297174 |
| 22 | 244009225 |
| 23 | 839101403 |
| 24 | 2898145437 |
| 25 | 10050549437 |
| 26 | 34985611467 |
| 27 | 122209803101 |
| 28 | 428285696895 |
| 29 | 1505491979826 |