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 | 3 |
| 2 | 15 |
| 3 | 165 |
| 4 | 2145 |
| 5 | 40755 |
| 6 | 1181895 |
| 7 | 43730115 |
| 8 | 2317696095 |
| 9 | 136744069605 |
| 10 | 8341388245905 |
| 11 | 558873012475635 |
| 12 | 46386460035477705 |
| 13 | 4685032463583248205 |
| 14 | 501298473603407557935 |
| 15 | 65670100042046390089485 |
| 16 | 9128143905844448222438415 |
| 17 | 1360093441970822785143323835 |
| 18 | 221695231041244113978361785105 |