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 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 0 |
| 6 | 1 |
| 7 | 6 |
| 8 | 63 |
| 9 | 616 |
| 10 | 6678 |
| 11 | 77868 |
| 12 | 978978 |
| 13 | 13216104 |
| 14 | 190899423 |
| 15 | 2939850914 |
| 16 | 48106651593 |
| 17 | 833848627248 |
| 18 | 15265844099324 |
| 19 | 294412707629208 |
| 20 | 5966764207952724 |
| 21 | 126793739418994416 |
| 22 | 2819296088257641741 |
| 23 | 65470320271760790078 |