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 | 6 |
| 4 | 57 |
| 5 | 683 |
| 6 | 9474 |
| 7 | 145815 |
| 8 | 2430393 |
| 9 | 43202448 |
| 10 | 810629805 |
| 11 | 15938815794 |
| 12 | 326653743510 |
| 13 | 6949638584208 |
| 14 | 153009877730525 |
| 15 | 3477623225388063 |
| 16 | 81429702521625843 |
| 17 | 1961136442605508341 |
| 18 | 48513571089988199157 |