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 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 3 |
| 5 | 9 |
| 6 | 53 |
| 7 | 465 |
| 8 | 9815 |
| 9 | 288601 |
| 10 | 19609857 |
| 11 | 1719287011 |
| 12 | 340800846539 |
| 13 | 88312098753293 |
| 14 | 52527897517470365 |
| 15 | 41335202747219808853 |
| 16 | 74965326513925821171199 |
| 17 | 179806473914469748125175893 |
| 18 | 992651698460472155144461591193 |