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 | 4 |
| 1 | 4 |
| 2 | 5 |
| 3 | 9 |
| 4 | 21 |
| 5 | 53 |
| 6 | 133 |
| 7 | 325 |
| 8 | 773 |
| 9 | 1797 |
| 10 | 4101 |
| 11 | 9221 |
| 12 | 20485 |
| 13 | 45061 |
| 14 | 98309 |
| 15 | 212997 |
| 16 | 458757 |
| 17 | 983045 |
| 18 | 2097157 |
| 19 | 4456453 |
| 20 | 9437189 |
| 21 | 19922949 |
| 22 | 41943045 |
| 23 | 88080389 |
| 24 | 184549381 |
| 25 | 385875973 |
| 26 | 805306373 |
| 27 | 1677721605 |
| 28 | 3489660933 |
| 29 | 7247757317 |