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 | 840 |
| 2 | 2040 |
| 3 | 4440 |
| 4 | 9240 |
| 5 | 25320 |
| 6 | 51000 |
| 7 | 117480 |
| 8 | 271320 |
| 9 | 765480 |
| 10 | 1531320 |
| 11 | 3721800 |
| 12 | 5956440 |
| 13 | 12295560 |
| 14 | 25086840 |
| 15 | 54141960 |
| 16 | 108284280 |
| 17 | 250301640 |
| 18 | 502213560 |
| 19 | 1007626440 |
| 20 | 2017856760 |
| 21 | 4039750920 |
| 22 | 8079502200 |
| 23 | 19596145800 |
| 24 | 44369345400 |
| 25 | 71495068200 |
| 26 | 115576350360 |
| 27 | 231152701080 |