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 | 3 |
| 4 | 19 |
| 5 | 201 |
| 6 | 3106 |
| 7 | 64522 |
| 8 | 1704795 |
| 9 | 55095601 |
| 10 | 2115975655 |
| 11 | 94466053541 |
| 12 | 4818194778101 |
| 13 | 276874057979927 |
| 14 | 17721751093252740 |
| 15 | 1251476983229057488 |
| 16 | 96724943665929684251 |
| 17 | 8125833302851782601185 |
| 18 | 737619034028749204655009 |
| 19 | 71975174880203583395021875 |