The twin composites may be defined by analogy with the twin primes as pairs of composite numbers (n, n + 2). Since all even number are trivially twin composites, it is natural to consider only odd twin composites. Since if n is odd, then n + 1 is even, it follows that odd twin composites always bracket an even number. The first few odd twin composites are (25, 27), (33, 35), (49, 51), (55, 57), (63, 65), (75, 77), (85, 87), (91, 93), (93, 95), ... (OEIS A269345 and A025583), whose bisections are given by 26, 34, 50, 56, 64, 76, 86, 92, 94, 116, 118, ... (A061673).

composite number | prime gaps | twin primes