OFFSET
0,4
COMMENTS
This sequence occurs in quantum mechanics, in the context of counting certain kinds of inseparable states in an n-qubit model.
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..1000
J. S. Pratt, Universality in the entanglement structure of ferromagnets, Phys. Rev. Lett. 93, 237205 (2004)
J. S. Pratt, Comments on this sequence
EXAMPLE
a(16) = 3 because there are three integers between 6 and 10.
MAPLE
a:= n-> max(0, ceil((n+sqrt(n))/2)-1-floor((n-sqrt(n))/2)):
seq(a(n), n=0..120); # Alois P. Heinz, Apr 02 2014
MATHEMATICA
a[n_] := If[IntegerQ[Sqrt[n]], Sum[1, {m, Ceiling[(n - Sqrt[n])/2] + 1, Floor[(n + Sqrt[n])/2] - 1}], Sum[1, {m, Ceiling[(n - Sqrt[n])/2], Floor[(n + Sqrt[n])/2]}]]
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Jeff S. Pratt (jpratt(AT)pas.rochester.edu), Sep 10 2003
EXTENSIONS
a(0)-a(1) prepended by Alois P. Heinz, Apr 02 2014
STATUS
approved