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 | 4 |
| 3 | 24 |
| 4 | 190 |
| 5 | 1860 |
| 6 | 21638 |
| 7 | 291158 |
| 8 | 4443556 |
| 9 | 75779580 |
| 10 | 1427272032 |
| 11 | 29409572808 |
| 12 | 657829667328 |
| 13 | 15868725580344 |
| 14 | 410543007882408 |
| 15 | 11336582934052104 |
| 16 | 332736828827893968 |
| 17 | 10342443317857993680 |
| 18 | 339343476195341474688 |