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 | 120 |
| 4 | 12960 |
| 5 | 332880 |
| 6 | 3868080 |
| 7 | 27767880 |
| 8 | 144278400 |
| 9 | 594347040 |
| 10 | 2055598560 |
| 11 | 6202551960 |
| 12 | 16774966560 |
| 13 | 41473626480 |
| 14 | 95135323920 |
| 15 | 204803912040 |
| 16 | 417515696640 |
| 17 | 811858751040 |
| 18 | 1514650599360 |
| 19 | 2724410748600 |
| 20 | 4743687388320 |
| 21 | 8022734847120 |
| 22 | 13217533726320 |
| 23 | 21265702652040 |
| 24 | 33484472926080 |
| 25 | 51695588642400 |
| 26 | 78382758698400 |
| 27 | 116888127197400 |