The complete organic molecule in the title dihydrate, C(20)H(22)N(4)O(4), is generated by crystallographic twofold symmetry, with two C atoms lying on the rotation axis. The symmetry unique pyridine ring forms a dihedral angle of 83.16 (8)° with the central benzene ring. In the crystal, inter-molecular N-H⋯O, O-H⋯N and O-H⋯O hydrogen bonds connect the components into a two-dimensional network l...

The title compound, C(19)H(12)F(2)N(2)O(2), a 2:1 product of the reaction of 3-fluoro-benzoyl-chloride and 2-amino-pyridine crystallizes with a disordered 3-fluoro-benzene ring adopting two conformations [ratio of occupancies 0.959 (4):0.041 (4)]. In the crystal structure, there are no classical hydrogen bonds and inter-actions comprise C-H⋯O in the form 2(C-H)⋯O=C [with motif R(2) (1)(5)]; C-H...

Letn ≡ k−1, 0 or 1 (mod k).An R̃MP(k, ; n,m) (resp. R̃MC(k, ; n,m)) is a resolvable packing (resp. covering)withmaximum (resp. minimum) possible number m of parallel classes which are mutually distinct, each parallel class consists of (n− k + 1)/k blocks of size k and one block of size n− k (n− k+ 1)/k , and its leave (resp. excess) is a simple graph. Such designs can be used to construct certain...