OFFSET
0,3
COMMENTS
In concurrency theory, a(n) is also the cumulated sizes of computation trees induced by interleaved concurrent processes of size n.
REFERENCES
O. Bodini, A. Genitrini and F. Peschanski. Enumeration and Random Generation of Concurrent Computations. In proc. 23rd International Meeting on Probabilistic, Combinatorial and Asymptotic Methods for the Analysis of Algorithms (AofA'12), Discrete Mathematics and Theoretical Computer Science, pp 83-96, 2012.
LINKS
O. Bodini, A. Genitrini, F. Peschanski, A Quantitative Study of Pure Parallel Processes, arXiv preprint arXiv:1407.1873, 2014
FORMULA
P-recurrence: (16*n-64*n^3)*a(n)+(12+72*n+112*n^2+32*n^3)*a(n+1)+(-26-62*n-4*n^3-36*n^2)*a(n+2)+(5+7*n+2*n^2)*a(n+3) = 0; a(0)=0; a(1)=1; a(2)=2.
a(n) ~ 2^(n-1/2) * n^(n-1) / exp(n-1). - Vaclav Kotesovec, Mar 08 2014
MATHEMATICA
Flatten[{0, RecurrenceTable[{-16*(-3+n)*(-7+2*n)*(-5+2*n)*a[-3+n]+4*(-5+2*n)*(3-12*n+4*n^2)*a[-2+n]-2*(28-23*n+2*n^3)*a[-1+n]+(-2+n)*(-1+2*n)*a[n]==0, a[1]==1, a[2]==2, a[3]==8}, a, {n, 1, 20}]}] (* Vaclav Kotesovec, Mar 08 2014 *)
PROG
(Python)
def a(n):
if n < 3:
return n
l = [0, 1, 2]
for i in range(n-2):
l[i%3] = ( (16*i-64*i**3)*l[i%3]+(12+72*i+112*i**2+32*i**3)*l[(i+1)%3]+(-26-62*i-4*i**3-36*i**2)*l[(i+2)%3] ) / (-5-7*i-2*i**2)
return l[i%3]
CROSSREFS
KEYWORD
nonn
AUTHOR
Antoine Genitrini, Mar 14 2013
STATUS
approved