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 | 1 |
| 2 | 5 |
| 3 | 35 |
| 4 | 315 |
| 5 | 3455 |
| 6 | 44590 |
| 7 | 660665 |
| 8 | 11035095 |
| 9 | 204904830 |
| 10 | 4183174520 |
| 11 | 93055783320 |
| 12 | 2238954627848 |
| 13 | 57903797748386 |
| 14 | 1601122732128779 |
| 15 | 47120734323344439 |
| 16 | 1470076408565099152 |
| 17 | 48449426629560437576 |
| 18 | 1681560512531504058350 |
| 19 | 61293054886119796799892 |