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A225381
Elimination order of the first person in a Josephus problem.
3
1, 2, 2, 4, 3, 5, 4, 8, 5, 8, 6, 11, 7, 11, 8, 16, 9, 14, 10, 18, 11, 17, 12, 23, 13, 20, 14, 25, 15, 23, 16, 32, 17, 26, 18, 32, 19, 29, 20, 38, 21, 32, 22, 39, 23, 35, 24, 47, 25, 38, 26, 46, 27, 41, 28, 53, 29, 44, 30, 53, 31, 47, 32, 64, 33, 50, 34, 60, 35
OFFSET
1,2
COMMENTS
In a Josephus problem such as A006257, a(n) is the order in which the person originally first in line is eliminated.
The number of remaining survivors after the person originally first in line has been eliminated, i.e., n-a(n), gives the fractal sequence A025480.
For the linear version, see A225489.
LINKS
Cristina Ballantine and Mircea Merca, Plane Partitions and Divisors, Symmetry (2024), Vol. 16, Iss. 5. See page 9.
Mircea Merca, Plane Partitions and a Problem of Josephus, Mathematics (2023), Vol. 11, Iss. 4996. See page 2.
FORMULA
a(n) = (n+1)/2 (odd n); a(n) = a(n/2) + n/2 (even n).
a(n) = n - A025480(n).
G.f.: Sum{n>=1} x^n/(1-x^A006519(n)). - Nicolas Nagel, Mar 19 2018
EXAMPLE
If there are 7 persons to begin with, they are eliminated in the following order: 2,4,6,1,5,3,7. So the first person (the person originally first in line) is eliminated as number 4. Therefore a(7) = 4.
MATHEMATICA
t = {1}; Do[AppendTo[t, If[OddQ[n], (n + 1)/2, t[[n/2]] + n/2]], {n, 2, 100}]; t (* T. D. Noe, May 17 2013 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Marcus Hedbring, May 17 2013
STATUS
approved