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 | 3 |
| 3 | 15 |
| 4 | 100 |
| 5 | 805 |
| 6 | 7442 |
| 7 | 76750 |
| 8 | 866818 |
| 9 | 10586499 |
| 10 | 138549918 |
| 11 | 1929878820 |
| 12 | 28459172110 |
| 13 | 442421488758 |
| 14 | 7225177328165 |
| 15 | 123586748434192 |
| 16 | 2208493015533530 |
| 17 | 41138303109509415 |
| 18 | 797178212982793708 |
| 19 | 16041390159326400966 |
| 20 | 334654194086236031816 |
| 21 | 7227174934846895031544 |