20 shortest unsolved problems

# Problem Difficulty Length
1 GCD Sum 2 5.5 320 chars
2 Gauss Squares 4.1 334 chars
3 Emag Eht Htiw Em Pleh 1.9 379 chars
4 Almost Pythagorean 6.1 389 chars
5 Datum 1.5 420 chars
6 Division 6.7 435 chars
7 Inverse Totient 6.8 451 chars
8 Einfalt Dæmi! 1.2 - 2.7 477 chars
9 Yet Another Divisor Problem 8.0 491 chars
10 Brahmagupta-Fibonacci 3.3 505 chars
11 Danish Date Format 1.5 512 chars
12 Primitive Roots 6.7 522 chars
13 How many 0's? 3.1 554 chars
14 Sumsets 6.8 562 chars
15 Knight Packing 1.2 565 chars
16 Reseto 2.1 567 chars
17 Multiplication Over Symmetric Difference 6.2 570 chars
18 Any Pythagorean Triple 2.0 571 chars
19 A Different List Game 8.7 574 chars
20 Skálagerð 1.6 578 chars
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