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 | 7 |
| 2 | 62 |
| 3 | 509 |
| 4 | 4092 |
| 5 | 32763 |
| 6 | 262138 |
| 7 | 2097145 |
| 8 | 16777208 |
| 9 | 134217719 |
| 10 | 1073741814 |
| 11 | 8589934581 |
| 12 | 68719476724 |
| 13 | 549755813875 |
| 14 | 4398046511090 |
| 15 | 35184372088817 |
| 16 | 281474976710640 |
| 17 | 2251799813685231 |
| 18 | 18014398509481966 |
| 19 | 144115188075855853 |
| 20 | 1152921504606846956 |
| 21 | 9223372036854775787 |