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Semprime triplets are series of three consecutive semiprimes. They can end in {1, 2, 3}, or {9, X, E}.

The 5 semiprime triplets up to 100 are:

{29, 2X, 2E}, {71, 72, 73}, {79, 7X, 7E}, {X1, X2, X3}, {E9, EX, EE}

Note that the 3 numbers before 100 are all semiprimes, also note that 70-7E has both the {1, 2, 3} triplet and the {9, X, E} triplet. Not much research has been done on semiprime sequences, but it is easy to see that it is impossible to have a sequence of 4 consecutive semiprimes because one will have to be a multiple of 4.

Semiprime triplets can also take the form of {s, s+3, s+6}. These triplets can end in {7, X, 1} or {E, 2, 5}. The first of these triplets (only one less than 100) are {97, 9X, X1} and {10E, 112, 115}.

See also[]

Prime number