Track / Stage 4 / 176 of 340 #436 of 1964

18. Find the number of the first type of circular permutations made from 2 $a$s, 2 $b$s, and 4 $c$s, where the 2 $a$s are not adjacent.

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A number or a short expression. Fractions can be typed as 3/2, and spacing doesn't matter.

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Official solution

18. 39 .

Source: NuminaMath-1.5, licensed Apache-2.0. Statement and solution reproduced as published; topic, difficulty and ordering added by this site.