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 | 7 |
| 3 | 19 |
| 4 | 73 |
| 5 | 361 |
| 6 | 2161 |
| 7 | 15121 |
| 8 | 120961 |
| 9 | 1088641 |
| 10 | 10886401 |
| 11 | 119750401 |
| 12 | 1437004801 |
| 13 | 18681062401 |
| 14 | 261534873601 |
| 15 | 3923023104001 |
| 16 | 62768369664001 |
| 17 | 1067062284288001 |
| 18 | 19207121117184001 |
| 19 | 364935301226496001 |
| 20 | 7298706024529920001 |
| 21 | 153272826515128320001 |