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 | 105 |
| 4 | 315 |
| 5 | 3465 |
| 6 | 45045 |
| 7 | 90090 |
| 8 | 765765 |
| 9 | 451035585 |
| 10 | 25508568085 |
| 11 | 411827311870584610 |
| 12 | 525058386770138717020639964850 |
| 13 | 528134692562568161116953143877712480332943632586669596900 |