1,2

We denote by U[7,n,m] the number of the cases that the first player gets killed in a Russian roulette game when 7 players use a gun with n-chambers and m-bullets. They never rotate the cylinder after the game starts. The chambers can be represented by the list {1,2,...,n}. We are going to calculate (0), (1),...(t) separately. (0) The first player gets killed when one bullet is in the first chamber and the remaining (m-1)-bullets are in {2,3,...,n}. We have binomial[n-1,m-1]-cases for this. (1) The first gets killed when one bullet is in the 8th chamber and the rest of the bullets are in {9,..,n}. We have binomial[n-8,m-1]-cases for this. We continue to calculate, and the last is (t), where t = Floor[(n-m)/7]. (t) The first gets killed when one bullet is in (7t+1)-th chamber and the remaining bullets are in {7t+2,...,n}. We have binomial[n-7t-1,m-1]-cases for this. Therefore U[7,n,m] = Sum[binomial[n-7z-1,m-1], for z = 0 to t, where t = Floor[(n-m)/7]. Let A[7,n] be the number of the cases that the first player gets killed when 7-player use a gun with n-chambers and the number of the bullets can be from 1 to n. Then A[7,n] = Sum[U[7,n,m], m = 1 to n]

Miyadera, R. "General Theory of Russian Roulette." Mathematica source.

Miyadera, R. Mathematical Theory of Magic Fruits Archimedes-lab.

R. Miyadera, General Theory of Russian Roulette, MathSource

R. Miyadera, Daisuke Minematsu, Satoshi Hashiba and Munetoshi Hashiba, Theory of Magic Fruits, Archimedes-labInteresting patterns of fractionshttp

a(n) = (2^(n + 6) - 2^(Mod[n - 1, 7]))/(2^7 - 1), where Mod[,7] is the remaining part of the number when divided by 7. In the followings we present the formula based on the theory we used to define our sequence as a Mathematica code. The above formula is a lot easier to use, but the Mathematica code has an important mathematical meaning in it.

If the number of chambers is 3, then the number of the bullets can be 1,2,3. The first one get killed when one bullet is in the first chamber, and the remaining bullets are in the second and the third chamber. All the cases is {{1, 0, 0}, {1, 1, 0}, {1, 0, 1}, {1, 1, 1}}, where we denote by 1 the chamber that contains the bullet. Therefore a(3) = 4.

U7[n_, m_] := Block[{t}, t = Floor[(n - m)/7]; Sum[Binomial[n - 1 - 7z, m - 1], {z, 0, t}]]; A7[n_] := Sum[U7[n, m], {m, 1, n}]; Table[A7[n], {n, 1, 30}]

Sequence in context: A079838 A109912 A079845 this_sequence A023422 A084638 A006211

Adjacent sequences: A117299 A117300 A117301 this_sequence A117303 A117304 A117305

nonn,uned

Tomohide Hashiba, Akihiro Hyogu, Hiroshi Matsui, Ryohei Miyadera, Yuta Nakagawa (miyadera1272000(AT)yahoo.co.jp), Apr 24 2006