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 | 0 |
| 2 | 2 |
| 3 | 10 |
| 4 | 44 |
| 5 | 196 |
| 6 | 876 |
| 7 | 4020 |
| 8 | 18766 |
| 9 | 89322 |
| 10 | 431758 |
| 11 | 2116220 |
| 12 | 10494080 |
| 13 | 52569504 |
| 14 | 265647586 |
| 15 | 1352621168 |
| 16 | 6933127446 |
| 17 | 35745747902 |
| 18 | 185256755454 |
| 19 | 964575991660 |
| 20 | 5043194697556 |
| 21 | 26467075595080 |
| 22 | 139375175511598 |
| 23 | 736228488297566 |
| 24 | 3900073083063348 |
| 25 | 20714052518640904 |