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 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 4 |
| 5 | 15 |
| 6 | 48 |
| 7 | 148 |
| 8 | 435 |
| 9 | 1250 |
| 10 | 3512 |
| 11 | 9726 |
| 12 | 26587 |
| 13 | 71975 |
| 14 | 193200 |
| 15 | 515051 |
| 16 | 1364896 |
| 17 | 3598794 |
| 18 | 9447028 |
| 19 | 24704031 |
| 20 | 64382465 |
| 21 | 167288460 |
| 22 | 433512724 |
| 23 | 1120719444 |
| 24 | 2891035926 |
| 25 | 7443225226 |
| 26 | 19129208972 |
| 27 | 49082742607 |
| 28 | 125752279124 |
| 29 | 321744111359 |
| 30 | 822165920924 |
| 31 | 2098475215237 |