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 | 31 |
| 4 | 252 |
| 5 | 2117 |
| 6 | 18546 |
| 7 | 164229 |
| 8 | 1469596 |
| 9 | 13229876 |
| 10 | 119712521 |
| 11 | 1087573357 |
| 12 | 9914033252 |
| 13 | 90633332870 |
| 14 | 830621140260 |
| 15 | 7628813061585 |
| 16 | 70200092854044 |
| 17 | 647070588612140 |
| 18 | 5973385906039684 |
| 19 | 55217660246861884 |
| 20 | 511054426374819184 |
| 21 | 4735208302827742549 |