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 | 0 |
| 5 | 3 |
| 6 | 4 |
| 7 | 15 |
| 8 | 42 |
| 9 | 131 |
| 10 | 438 |
| 11 | 1467 |
| 12 | 5204 |
| 13 | 18687 |
| 14 | 69306 |
| 15 | 261473 |
| 16 | 1007328 |
| 17 | 3943155 |
| 18 | 15679474 |
| 19 | 63199785 |
| 20 | 257983836 |
| 21 | 1065186381 |
| 22 | 4444618518 |
| 23 | 18725820855 |
| 24 | 79603364236 |
| 25 | 341206137453 |
| 26 | 1473818915658 |
| 27 | 6411853714819 |
| 28 | 28082121491796 |
| 29 | 123764682835371 |
| 30 | 548675459164202 |