Suppose the values of [x] in column A from A2, the value of [a] in cell E2.
The matrix formula is then
=2/PI()*SINH($E$2*PI())*(1/(2*$E$2)+SUM(((-1)^ROW($A$1:$A$1000)/($E$2^2+ROW($A$1:$A$1000)^2))*($E$2* COS(ROW($A$1:$A$1000)*A2)-ROW($A$1:$A$1000)*SIN(ROW($A$1:$A$1000)*A2))))
Do not forget to confirm the formula with Ctrl + Shift + Enter
[k] is not a constant. It ranges from 1 to infinity.
In the formula [k] belongs to the interval [1..1000] and is ROW($A$1:$A$1000).
For greater accuracy must use higher values. Ex: ROW($A$1:$A$65000).
See de file
Best regards.
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