SOLUTION: Find the sum of the infinite series (1 + 2 + 3 + 4 + .... + r-1) divided by r! where r is from {{{ 2 to inf }}}? [Note: Here r! means factorial of r]

Question 1184396: Find the sum of the infinite series (1 + 2 + 3 + 4 + .... + r-1) divided by r! where r is from ?
[Note: Here r! means factorial of r]
Answer by ikleyn(52903) (Show Source): You can put this solution on YOUR website!
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Find the sum of the infinite series (1 + 2 + 3 + 4 + .... + r-1) divided by r! where r is from
~~~~~~~~~~~~~~

The sum   1 + 2 + 3 + . . . + (r-1)  is  .


This sum divided by  r! is  .


So, the problem asks about this sum  .


It is the same as the expression  .


The last expression value is  ,  where  "e"  is the base of natural logarithms.


ANSWER.  The requested sum is equal to   =  = 1.35914  (rounded).

Solved, answered and explained.

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