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 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 7 |
| 5 | 31 |
| 6 | 121 |
| 7 | 806 |
| 8 | 5706 |
| 9 | 40902 |
| 10 | 345444 |
| 11 | 3627834 |
| 12 | 44916840 |
| 13 | 473882124 |
| 14 | 5607925896 |
| 15 | 73429902300 |
| 16 | 1169960275680 |
| 17 | 18289685306640 |
| 18 | 315392669158416 |
| 19 | 5046227338720884 |
| 20 | 98328156602878800 |
| 21 | 1862418125263338720 |
| 22 | 36536960773307025360 |
| 23 | 777453614193997039320 |