Answers

2016-06-15T03:10:48+08:00
Formula of Harmonic Sequence
HS = 1 / an
an is the arithmetic sequence formula where
an = a1 + (n-1)d
where 
an is the nth term
a1 is first term
n is the exponent of the term
d is the common difference
so from your example
a1 is 11
a2 is 15 
a3 is 19
a4 is 23
so we need to get the next term a5
from the formula
d = 15 - 11
d = 4
HS = 1 / an
      = 1/ a1 + ( n - 1 ) d
      = 1/11 + (5 - 1) (4)
HS = 1 / 27
so the next term is 1 /27
1 5 1