recursive sums

[Guest]

I would like to know how to generate a column which can fill the cells in the
order: FACT(1) ; FACT(2); FACT(3)... etcetera. Apparently it will not work by
dragging the cells down.

Also, I need to generate a cell which can perform the function of:
f(x) = e^x = 1 + (1/1!)*x + (1/2!)*x^2 + (1/3!)*x^3... which by means is the
exp fn of the maclaurin series.

any help or suggestions is very much appreciated.

 

[Guest]

For you first question

If you are starting in cell A1:

=FACT(ROWS(A$1:A1))

and copy down.

 

[Bob Phillips]

=FACT(ROW(A1))

--

HTH

RP
(remove nothere from the email address if mailing direct)

 

[Guest]

Won't that throw an error if the first row or column is deleted (assuming the
table does not start in cell A1)?

 

[Dana DeLouis]

Hi. Just to add....
In A1, you could enter this for the first part of the equation.
=1/FACT(ROW()-1)

and drag down to say A10. (ie Start w/ Fact(0) )

Then your Series can be calculated as...

=SERIESSUM(1,0,1,A1:A10)

Returns a number close to =EXP(1)
HTH :>)

 

[Aladin Akyurek]

Won't that throw an error if the first row or column is deleted (assuming the
table does not start in cell A1)?


:

ROW(A1) is not an idiom one would choose if one is concerned with
robustness.

=FACT(ROWS($1:1))

entered in A1, would be robust against inserting rows/columns before the
formula cell and against deleting the first formula row.

 

[Hans Knudsen]

Just to add one more:
Put n (= number of terms of the sequence f(x)) in A1 and x in A2 then enter the following array formula:
=1+SUM((FACT((ROW(INDIRECT("1"&":"&A1))))^-1)*A2^ROW(INDIRECT("1"&":"&A1)))
(Note that n > 21 will not change the result).

Hans Knudsen