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 | 3 |
| 2 | 15 |
| 3 | 94 |
| 4 | 660 |
| 5 | 4959 |
| 6 | 38995 |
| 7 | 316875 |
| 8 | 2639754 |
| 9 | 22423292 |
| 10 | 193484208 |
| 11 | 1691190228 |
| 12 | 14942632450 |
| 13 | 133242614565 |
| 14 | 1197520200870 |
| 15 | 10836727044255 |
| 16 | 98656011543816 |
| 17 | 902936341411170 |
| 18 | 8303218554134769 |
| 19 | 76679352910367832 |
| 20 | 710839322080978272 |
| 21 | 6612557820697157410 |