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 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 28 |
| 5 | 301 |
| 6 | 4466 |
| 7 | 84974 |
| 8 | 1974904 |
| 9 | 54233540 |
| 10 | 1718280152 |
| 11 | 61695193880 |
| 12 | 2475688513024 |
| 13 | 109797950475448 |
| 14 | 5333253012414224 |
| 15 | 281576039542538368 |
| 16 | 16055279332196218624 |
| 17 | 983264280857581866112 |
| 18 | 64369946360185677026048 |
| 19 | 4485859513184032011682304 |
| 20 | 331558482325457407154881024 |