The title compound, C(10)H(10)N(8), resides on a crystallographic symmetry center and features an essentially planar mol-ecule [r.m.s. deviation = 0.278 (1) Å]. In the C=N-N=C fragment, the C=N distance is 1.3017 (18) Å and the N-N distance is 1.403 (2) Å. In the crystal, adjacent mol-ecules are linked by N-H⋯N hydrogen bonds into a three-dimensional network.

Let C be a plane convex body. For arbitrary points , denote by , n a b E  ab the Euclidean length of the line-segment . Let be a longest chord of C parallel to the line-segment . The relative distance between the points and is the ratio of the Euclidean distance between and b to the half of the Euclidean distance between and . In this note we prove the triangle inequality in with the relative ...

The emph{Harary index} $H(G)$ of a connected graph $G$ is defined as $H(G)=sum_{u,vin V(G)}frac{1}{d_G(u,v)}$ where $d_G(u,v)$ is the distance between vertices $u$ and $v$ of $G$. The Steiner distance in a graph, introduced by Chartrand et al. in 1989, is a natural generalization of the concept of classical graph distance. For a connected graph $G$ of order at least $2$ ...

There is a natural greedy approach to construct a code of distance at least d: start with any codeword, and keep on adding codewords which have distance at least d from all previously chosen codewords, until we can proceed no longer. Suppose this procedure halts after picking a code C. Then Hamming balls in {0, 1, . . . , q−1}n of radius d−1 centered at the codewords of C must cover the whole s...