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 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 4 |
| 4 | 52 |
| 5 | 532 |
| 6 | 4772 |
| 7 | 44624 |
| 8 | 413332 |
| 9 | 3704668 |
| 10 | 32312456 |
| 11 | 277318708 |
| 12 | 2365831332 |
| 13 | 20023322874 |
| 14 | 168065885292 |
| 15 | 1401084600204 |
| 16 | 11617827516556 |
| 17 | 95910742322858 |
| 18 | 788559509624036 |
| 19 | 6459527069162538 |
| 20 | 52742304806108492 |
| 21 | 429408151732020490 |
| 22 | 3487057360672870112 |