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 | 1 |
| 3 | 3 |
| 4 | 12 |
| 5 | 60 |
| 6 | 256 |
| 7 | 1008 |
| 8 | 4032 |
| 9 | 16320 |
| 10 | 65536 |
| 11 | 261888 |
| 12 | 1047552 |
| 13 | 4193280 |
| 14 | 16777216 |
| 15 | 67104768 |
| 16 | 268419072 |
| 17 | 1073725440 |
| 18 | 4294967296 |
| 19 | 17179803648 |
| 20 | 68719214592 |
| 21 | 274877644800 |
| 22 | 1099511627776 |
| 23 | 4398045462528 |
| 24 | 17592181850112 |
| 25 | 70368739983360 |
| 26 | 281474976710656 |
| 27 | 1125899890065408 |
| 28 | 4503599560261632 |
| 29 | 18014398442373120 |