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 | 1 |
| 2 | 4 |
| 3 | 21 |
| 4 | 128 |
| 5 | 819 |
| 6 | 5460 |
| 7 | 37449 |
| 8 | 262144 |
| 9 | 1864128 |
| 10 | 13421772 |
| 11 | 97612893 |
| 12 | 715827840 |
| 13 | 5286113595 |
| 14 | 39268272420 |
| 15 | 293203100463 |
| 16 | 2199023255552 |
| 17 | 16557351571215 |
| 18 | 125099989647360 |
| 19 | 948126237341157 |
| 20 | 7205759403792768 |
| 21 | 54901024028884989 |
| 22 | 419244183493398900 |
| 23 | 3208129404123400281 |
| 24 | 24595658764945981440 |