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 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 0 |
| 6 | 20 |
| 7 | 210 |
| 8 | 1400 |
| 9 | 7560 |
| 10 | 36120 |
| 11 | 159390 |
| 12 | 1035100 |
| 13 | 17082780 |
| 14 | 329893564 |
| 15 | 5336661330 |
| 16 | 73265956400 |
| 17 | 889068944400 |
| 18 | 9968073461616 |
| 19 | 112902000191334 |
| 20 | 1531070090032500 |
| 21 | 27610559023112100 |
| 22 | 586336131631313140 |
| 23 | 12550716321612658266 |
| 24 | 254052845940651258600 |