Loop-space cohomology quotients
Let be the based loop space of the -sphere, and let with its usual cup product and cohomological grading. For a -element subset of , define . For each , let be the canonical inclusion into the summand.
Define to be the subgroup of generated by all elements , where , and and are homogeneous elements of of positive cohomological degree with . In other words, is the direct sum, over , of the subgroup of generated by all decomposable cup products in degree .
For an abelian group and a prime , let denote the -primary torsion subgroup of , meaning the subgroup of elements whose order is a power of . The trivial group is considered cyclic. Call admissible if, for every prime , the group is cyclic.
Let , which is prime. Determine the number of admissible -element subsets of such that , and report the answer modulo .