OFFSET
0,2
COMMENTS
The polynomials p_n(x) are monic.
The coefficient of x^(n-1) in p_n(x) is A022264(n).
For positive integers a, b, we have b!*4^b*p_a(b) = a!*4^a*p_b(a).
The coefficients are conjectured to be positive integers.
LINKS
M. Harned and M. Rittenberg, NIM Counting, Part 2, Girls' Angle Bulletin, Vol. 10, No. 5 (2017), 6-10.
FORMULA
p_n(x) = n!*Sum_{k=0..n} (4^(n-k-1)*(binomial(n-1,k+1) + 4*binomial(n-1,k) + 4*binomial(n-1,k-1))*binomial(x-1,k)).
EXAMPLE
p_0(x) = 1 since a Nim game with one stack with x tokens can be played out in 2^(x-1) ways (since each way is equivalent to placing dividers into some of the x-1 spaces between tokens).
p_2(2) = 26 + 13*2 + 2^2 = 56 since there are 2^(2-2-1)*56/2! = 14 ways to play out a Nim game that starts with two stacks with two tokens in each stack:
(2,2)->(2,1)->(2,0)->(1,0)->(0,0)
(2,2)->(2,1)->(2,0)->(0,0)
(2,2)->(2,1)->(1,1)->(1,0)->(0,0)
(2,2)->(2,1)->(1,1)->(0,1)->(0,0)
(2,2)->(2,1)->(0,1)->(0,0)
(2,2)->(2,0)->(1,0)->(0,0)
(2,2)->(2,0)->(0,0)
(2,2)->(1,2)->(1,1)->(1,0)->(0,0)
(2,2)->(1,2)->(1,1)->(0,1)->(0,0)
(2,2)->(1,2)->(0,2)->(0,1)->(0,0)
(2,2)->(1,2)->(0,2)->(0,0)
(2,2)->(1,2)->(1,0)->(0,0)
(2,2)->(0,2)->(0,1)->(0,0)
(2,2)->(0,2)->(0,0)
CROSSREFS
KEYWORD
AUTHOR
Jane Wang, Jul 02 2017
STATUS
approved