Digital root number is the number mod 11 (Ɛ), for example, 1972 is 1 + 9 + 7 + 2 = 19 = 17 which is 1 + 7 = 8, while in decimal the root of the same number (3110) is 5; and in base 16 a digital root of a number is the number mod 15 (0xF), for example, 0x7DF is 7 + 13 + 15 = 35 = 0x23 which is 2 + 3 = 5, while in decimal the root of the same number (2015) is 8. Digital roots form an important mechanic in the visual novel adventure
Root system arrangement of the tetrahedral-octahedral honeycomb. The A root system (as well as the other rank-three root systems) may be modeled in the Zometool Construction set. In general, the A root lattice is the vertex arrangement of the "n"-dimensional simplectic honeycomb. Let "E" = R, and let Φ consist of all integer vectors in "E" of length 1 or . The total number of roots is 2"n". One choice of simple roots is: α = e – e, for 1 ≤ i ≤ n – 1 (the above choice of simple roots for A), and the shorter root α = e.