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 | 4 |
| 3 | 24 |
| 4 | 160 |
| 5 | 1136 |
| 6 | 8420 |
| 7 | 64224 |
| 8 | 499984 |
| 9 | 3952928 |
| 10 | 31634724 |
| 11 | 255682432 |
| 12 | 2083562368 |
| 13 | 17097573344 |
| 14 | 141143273396 |
| 15 | 1171240794072 |
| 16 | 9763809318912 |
| 17 | 81724975129664 |
| 18 | 686539343850164 |