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) |
|---|---|
| 0 | 1 |
| 1 | 5 |
| 2 | 18 |
| 3 | 67 |
| 4 | 260 |
| 5 | 1029 |
| 6 | 4102 |
| 7 | 16391 |
| 8 | 65544 |
| 9 | 262153 |
| 10 | 1048586 |
| 11 | 4194315 |
| 12 | 16777228 |
| 13 | 67108877 |
| 14 | 268435470 |
| 15 | 1073741839 |
| 16 | 4294967312 |
| 17 | 17179869201 |
| 18 | 68719476754 |
| 19 | 274877906963 |
| 20 | 1099511627796 |
| 21 | 4398046511125 |
| 22 | 17592186044438 |
| 23 | 70368744177687 |