1 + 50% + 1/3 + 1/4 +.... + 1/n
There is no simple closed form. But a rough estimate is given by
$$sum_r=1^n frac1r approx int_1^n fracdxx = log n $$
So as a ball park estimate, you know that the sum is roughly $log n$. For more precise estimate you can refer to Euler"s Constant.
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There is no simple expression for it.
But it is encountered so often that it is usually abbreviated khổng lồ $H_n$ và known as the $n$-th Harmonic number.
There are various approximations and other relations which you can find in Wikipedia under Harmonic Number or in the question Jose Santos referenced in the comments.
For example, $$H_n=G_n-(n+1)lfloorfracG_nn+1 floor$$ where $$G_n=fracn+(n+1)!choose n-1(n+1)!$$
But that kind of thing is more of a curiosity than a useful expression!
One can write$$1+frac12+frac13+cdots+frac1n=gamma+psi(n+1)$$where $gamma$ is Euler"s constant & $psi$ is the digamma function.
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Of course, one reason for creating the digamma function is to make formulaelike this true.
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how lớn find a sum of numbers in a sequence when some intermediate terms are not taken in to consideration?
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