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 | 3 |
| 2 | 15 |
| 3 | 117 |
| 4 | 1158 |
| 5 | 12930 |
| 6 | 154986 |
| 7 | 1947582 |
| 8 | 25317009 |
| 9 | 337610451 |
| 10 | 4592807895 |
| 11 | 63488144109 |
| 12 | 889226772132 |
| 13 | 12592147132572 |
| 14 | 179982549300948 |
| 15 | 2593187073716460 |
| 16 | 37622924436008574 |
| 17 | 549178914689660106 |
| 18 | 8059539548880228138 |
| 19 | 118846096104074358942 |
| 20 | 1760035125442960123992 |