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 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 2 |
| 5 | 5 |
| 6 | 15 |
| 7 | 41 |
| 8 | 124 |
| 9 | 369 |
| 10 | 1132 |
| 11 | 3491 |
| 12 | 10984 |
| 13 | 34768 |
| 14 | 111514 |
| 15 | 360560 |
| 16 | 1176797 |
| 17 | 3870389 |
| 18 | 12829765 |
| 19 | 42829894 |
| 20 | 143980892 |
| 21 | 487227611 |
| 22 | 1659499566 |
| 23 | 5688046485 |
| 24 | 19617965938 |
| 25 | 68078878268 |
| 26 | 237694501644 |
| 27 | 834946053269 |
| 28 | 2950683815028 |
| 29 | 10490767818951 |
| 30 | 37524169403930 |