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 | 3 |
| 2 | 9 |
| 3 | 21 |
| 4 | 47 |
| 5 | 103 |
| 6 | 223 |
| 7 | 479 |
| 8 | 1023 |
| 9 | 2175 |
| 10 | 4607 |
| 11 | 9727 |
| 12 | 20479 |
| 13 | 43007 |
| 14 | 90111 |
| 15 | 188415 |
| 16 | 393215 |
| 17 | 819199 |
| 18 | 1703935 |
| 19 | 3538943 |
| 20 | 7340031 |
| 21 | 15204351 |
| 22 | 31457279 |
| 23 | 65011711 |
| 24 | 134217727 |
| 25 | 276824063 |
| 26 | 570425343 |
| 27 | 1174405119 |
| 28 | 2415919103 |
| 29 | 4966055935 |