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 | -1 |
| 2 | 3 |
| 3 | 4 |
| 4 | 21 |
| 5 | 45 |
| 6 | 144 |
| 7 | 351 |
| 8 | 987 |
| 9 | 2516 |
| 10 | 6765 |
| 11 | 17533 |
| 12 | 46368 |
| 13 | 120927 |
| 14 | 317811 |
| 15 | 830820 |
| 16 | 2178309 |
| 17 | 5699693 |
| 18 | 14930352 |
| 19 | 39079807 |
| 20 | 102334155 |
| 21 | 267892404 |
| 22 | 701408733 |
| 23 | 1836254589 |
| 24 | 4807526976 |
| 25 | 12586118975 |
| 26 | 32951280099 |
| 27 | 86267178436 |
| 28 | 225851433717 |
| 29 | 591285701421 |
| 30 | 1548008755920 |