Friday, 1 July 2016

sequences and series - Approximation of Sum Containing a Product



Given the sum, kn=1j=0jr=01n+rk I am trying to find an integral approximation, but any other approximation method would also be a good start. The obviously tricky part about this sum is the product it contains, but alas using the Stirling factorial approximation technique (turning the product into a sum with logarithms) has led me nowhere. Any help would be greatly appreciated.


Answer



Term n is



Tn=j=0jr=01n+rk=kn/k1e1/k(Γ(nk)Γ(nk,1k))
If you want an integral, you can represent this as
Tn=e1/kk10et/ktn/k1dt

For large k, you can approximate e(1t)/k1+(1t)/k
making this
Tnk+n+1n(k+n)
and then your expression
kn=1Tnln(k)+γ


No comments:

Post a Comment

real analysis - How to find limhrightarrow0fracsin(ha)h

How to find lim without lhopital rule? I know when I use lhopital I easy get $$ \lim_{h\rightarrow 0}...