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 | 3 |
| 3 | 15 |
| 4 | 132 |
| 5 | 588 |
| 6 | 5031 |
| 7 | 22347 |
| 8 | 191064 |
| 9 | 848616 |
| 10 | 7255419 |
| 11 | 32225079 |
| 12 | 275514876 |
| 13 | 1223704404 |
| 14 | 10462309887 |
| 15 | 46468542291 |
| 16 | 397292260848 |
| 17 | 1764580902672 |
| 18 | 15086643602355 |
| 19 | 67007605759263 |
| 20 | 572895164628660 |
| 21 | 2544524437949340 |
| 22 | 21754929612286743 |
| 23 | 96624921036315675 |