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 | 0 |
| 2 | -2 |
| 3 | -3 |
| 4 | 20 |
| 5 | 115 |
| 6 | -306 |
| 7 | -6307 |
| 8 | -6616 |
| 9 | 462663 |
| 10 | 2956130 |
| 11 | -38945951 |
| 12 | -656504388 |
| 13 | 2325876683 |
| 14 | 145820995670 |
| 15 | 562691968005 |
| 16 | -33452317341616 |
| 17 | -449954883966065 |
| 18 | 7055017491780810 |
| 19 | 233802046526955497 |
| 20 | -571834988279277340 |
| 21 | -112474674691684827501 |