Step 1:
\The differential equation is
.
Assume there is a solution of the power series form 
Determine the derivative of the above solution function with respect to
.

Substitute
in .

Change
to
in sigma notation

The above expression is zero when
and coefficient of
is zero.
This will result
,
and 

is a recursive relation.
Find coefficients for some values of
.
value | \
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Substitute above values in 

From the above expression 3 multiples of coefficients only remained
\we can write
.
Rewrite the sum as
.
Maclaurin series is
.
write the sum in the exponential form
\
Solution:
\Solution of the differential equation
is 