> proj(4,h,tang): # need tangentbundle for chi
i1 : X = abstractProjectiveSpace'(4,base n,VariableName => h)
o1 = X
o1 : a flag bundle with subquotient ranks {4, 1}
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> F:=sheaf(2,[5*h,10*h^2]): # defines the Horrocks-Mumford bundle
i2 : F = abstractSheaf(X, Rank => 2, ChernClass => 1 + 5*h + 10*h^2)
o2 = F
o2 : an abstract sheaf of rank 2 on X
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> chi(F&*o(n*h)); # computes chi of its twists
4 3 125 2
1/12 n + 5/3 n + --- n + 125/6 n + 2
12
i3 : chi (F ** OO(n*h))
1 4 5 3 125 2 125
o3 = --n + -n + ---n + ---n + 2
12 3 12 6
o3 : QQ[n]
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