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 | 1 |
| 3 | 4 |
| 4 | 12 |
| 5 | 42 |
| 6 | 135 |
| 7 | 500 |
| 8 | 1797 |
| 9 | 6885 |
| 10 | 26612 |
| 11 | 105561 |
| 12 | 423734 |
| 13 | 1726531 |
| 14 | 7101261 |
| 15 | 29486169 |
| 16 | 123341520 |
| 17 | 519422274 |
| 18 | 2199966624 |
| 19 | 9365714175 |
| 20 | 40052639066 |
| 21 | 171985425594 |
| 22 | 741214499791 |
| 23 | 3205096564624 |
| 24 | 13901238793616 |
| 25 | 60460193311425 |
| 26 | 263627546862787 |
| 27 | 1152207975128287 |