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 | 1 |
| 3 | -2 |
| 4 | 4 |
| 5 | -11 |
| 6 | 55 |
| 7 | -359 |
| 8 | 2359 |
| 9 | -15230 |
| 10 | 100840 |
| 11 | -716555 |
| 12 | 5580145 |
| 13 | -47230091 |
| 14 | 425472229 |
| 15 | -4013326982 |
| 16 | 39379161136 |
| 17 | -402010392971 |
| 18 | 4279164575167 |
| 19 | -47533936734179 |
| 20 | 550239127112107 |
| 21 | -6618018093867506 |
| 22 | 82447377648018700 |
| 23 | -1061324336149876667 |
| 24 | 14095604842846277617 |