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Algebra
umang rathi's Avatar
umang rathi
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25 Feb 2007 15:10:25 IST
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summation of n factorial
None

solve this summation of n factorial
[ 0][n ]n!


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ankur khurana's Avatar

ankur khurana
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26 Feb 2007 12:18:00 IST
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(n+1)!/n -1
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fatafati
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26 Feb 2007 13:51:42 IST
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That's incorrect answer. Check by taking different values of n.
But nice attempt !!
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Sachin Batwani
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26 Feb 2007 13:57:18 IST
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Its (n+1)! - 1!
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umang rathi's Avatar

umang rathi
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26 Feb 2007 17:40:48 IST
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i am sorry but i also dont know answer
if any 1 gives answer plz justify it
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Abhijith
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26 Feb 2007 17:57:13 IST
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The sum-of-factorials function is defined by
S_1(n) = sum_(k==1)^(n)k!
 
= (-e+Ei(1)+pii+E_(n+2)(-1)Gamma(n+2))/e
 
= (-e+Ei(1)+R[E_(n+2)(-1)]Gamma(n+2))/e,
where Ei(z) is the exponential integral. Ei(1) approx 1.89512 E_n is the En Function, R[z] is the real part of z, and i is the imaginary number. The first few values are 1, 3, 9, 33, 153, 873, 5913, 46233, 409113, ...
 
but why do you need this? I am sure no problem of IIT level would require you to remember the above formula.
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ankur khurana's Avatar

ankur khurana
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26 Feb 2007 18:36:37 IST
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my answer may be wrong but method is correct
do you know about putting first and last value by breaking terms

well if you i can explain
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Bipin Dubey's Avatar

Bipin Dubey
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Joined: 23 Jan 2007
Posts: 7942
26 Feb 2007 19:26:37 IST
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konichiwa2x has already writen the expression for the sum of factorials.
If you want to gain knowedge on this topic you can refer to the link :
 
 
@ sachin_batwani,  the summation of (r).(r!) gives (n+1)! - 1  and not of r!.
 
Best Wishes
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