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 | 1 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 0 |
| 6 | 1 |
| 7 | 3 |
| 8 | 7 |
| 9 | 21 |
| 10 | 57 |
| 11 | 159 |
| 12 | 435 |
| 13 | 1217 |
| 14 | 3400 |
| 15 | 9633 |
| 16 | 27413 |
| 17 | 78733 |
| 18 | 227489 |
| 19 | 661984 |
| 20 | 1937211 |
| 21 | 5701733 |
| 22 | 16865522 |
| 23 | 50126650 |
| 24 | 149627241 |
| 25 | 448448400 |
| 26 | 1349060262 |
| 27 | 4072508115 |
| 28 | 12333762442 |
| 29 | 37466367898 |
| 30 | 114133581762 |