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 | 0 |
| 1 | 1 |
| 2 | 4 |
| 3 | 19 |
| 4 | 112 |
| 5 | 801 |
| 6 | 6756 |
| 7 | 65563 |
| 8 | 717760 |
| 9 | 8729857 |
| 10 | 116570980 |
| 11 | 1693096131 |
| 12 | 26548383984 |
| 13 | 446689827169 |
| 14 | 8023582921732 |
| 15 | 153192673528651 |
| 16 | 3097301219335936 |
| 17 | 66095983547942913 |
| 18 | 1484384376886189380 |
| 19 | 34991710162280602867 |
| 20 | 863797053818651591920 |
| 21 | 22282392569877969167521 |