Mathematica 11.3.0.0 Windows 10 64
Can anybody verify that in the following code the FindCycle statement either aborts with the result: "$Aborted[]" or it kills the Kernel outright.
ma = 300; da1 = Flatten[Table[ {(1 + 2 a1)^2/2 + (1 + 2 a2)^2/2, 2 (a2 (a2 + 1) - a1 - a1^2)} , {a2, ma}, {a1, 0, Floor[1/2 (-1 + Sqrt[-1 + 4 a2 + 4 a2^2])]}], 1]; da2 = Flatten[Table[ {(a1^2 + a2^2) 2, (a2^2 - a1^2) 2} , {a2, ma}, {a1, a2 - 1}], 1]; da = Transpose[Join[da1, da2]]; gr = Graph [Thread[da[[1]] -> da[[2]]]]; FindCycle[gr]