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 | 21 |
| 3 | 83 |
| 4 | 321 |
| 5 | 1235 |
| 6 | 4761 |
| 7 | 18443 |
| 8 | 71841 |
| 9 | 281315 |
| 10 | 1106601 |
| 11 | 4369403 |
| 12 | 17304561 |
| 13 | 68694995 |
| 14 | 273202041 |
| 15 | 1088057963 |
| 16 | 4337948481 |
| 17 | 17308878275 |
| 18 | 69106635081 |
| 19 | 276039644123 |
| 20 | 1102997363601 |
| 21 | 4408504767155 |
| 22 | 17623562909721 |
| 23 | 70462878967883 |