

A086520


Number of integers strictly greater than (nsqrt(n))/2 and strictly less than (n+sqrt(n))/2.


2



0, 0, 1, 2, 1, 2, 3, 2, 3, 2, 3, 4, 3, 4, 3, 4, 3, 4, 5, 4, 5, 4, 5, 4, 5, 4, 5, 6, 5, 6, 5, 6, 5, 6, 5, 6, 5, 6, 7, 6, 7, 6, 7, 6, 7, 6, 7, 6, 7, 6, 7, 8, 7, 8, 7, 8, 7, 8, 7, 8, 7, 8, 7, 8, 7, 8, 9, 8, 9, 8, 9, 8, 9, 8, 9, 8, 9, 8, 9, 8, 9, 8, 9, 10, 9, 10, 9, 10, 9, 10, 9, 10, 9, 10, 9, 10, 9, 10, 9, 10, 9, 10
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OFFSET

0,4


COMMENTS

This sequence occurs in quantum mechanics, in the context of counting certain kinds of inseparable states in an nqubit model.


LINKS



EXAMPLE

a(16) = 3 because there are three integers between 6 and 10.


MAPLE

a:= n> max(0, ceil((n+sqrt(n))/2)1floor((nsqrt(n))/2)):


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



STATUS

approved



