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For questions that specifically ask for determining a closed form of equations, integrals etc.

0 votes

looking for f(x) in f(x) = a.exp((x-f(x))/b)

According to Maple: so:=solve( f(x)-exp(( x - f(x)) /B ),f(x));latex(so); $$ f(x) =B{\it LambertW} \left( {{\rm e}^{{\frac {x}{B}}}}{B}^{-1} \right) $$ And for the title: so:=solve( f(x)-A …
joro's user avatar
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2 votes
1 answer
529 views

Conjectured closed form for definite integral

Let $K(x)$ be the complete elliptic integral of the first kind (the argument is the parameter $m = k^2$). Let $$ A = \int_0^1 \arcsin(K(x)) dx$$ With precision $1000$ decimal digits $\Re A = \frac{\ …
joro's user avatar
  • 25.4k
2 votes

Does this equation has a closed-form solution for $t$? ($(1-p)\sum_{i=0}^{n}t^i = p\sum_{i=0...

Too long for comment, here is partial answer for $n=5$ per R B's request. According to Maple: n:=5:q:=(1-p)*sum(t^i,i=0..n)-p*sum( (1-t)^i,i=0 .. n):so:=solve(q,t): so[1] and so[2] are complex and …
joro's user avatar
  • 25.4k
6 votes
Accepted

sum of integral part of n/k

For questions like this searching for the first few terms in OEIS might help 3, 5, 8, 10, 14, 16, 20, 23, 27, 29, 35, 37, 41 This is A006218. There are a lot of references and bounds for the sum. I …
joro's user avatar
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1 vote
1 answer
315 views

Is this long closed form for pi trivial?

With the help of wolfram alpha we got very long closed form for $\pi$ in terms of algebraic numbers, logarithms of algebraic numbers and $cot^{-1},coth^{-1}$ which can be expressed as logarithms. From …
joro's user avatar
  • 25.4k
4 votes
3 answers
1k views

Surprisingly long closed form for simple series

For natural $A$ define $$ f(A)=\sum_{n=1}^\infty \frac{1}{A^n}\left(\frac{1}{An+1}- \frac{1}{An+A-1}\right)$$ $f(A)$ is BBP (Bailey-Borwein-Plouffe) formula and allows digit extraction in base $A$. Fo …
joro's user avatar
  • 25.4k
-2 votes
1 answer
171 views

Simple closed form for $\int \lfloor x \rfloor dx$? [closed]

Wolfram Alpha claims there is no closed form in terms of standard funcions for $\int \lfloor x \rfloor dx$ but we believe we found simple closed form agreeing with experimental data. Define $i_1(x)=x …
joro's user avatar
  • 25.4k
3 votes
1 answer
546 views

Is there real or complex analytic function whose positive real zeros are the primes?

Related to this question Q1 Is there real or complex analytic function $f(x)$ such that its positive real zeros are the primes and it is given in closed form of compositions of already named function …
joro's user avatar
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0 votes
2 answers
273 views

Closed form for $\sum_{i=1}^n{a^{i^2}}$

Let $a$ be an element of some ring or field, possibly finite. Is there closed form for $\sum_{i=1}^n{a^{i^2}}$? sage and wolframalpha couldn't solve it. If $a$ is primitive n-th root of unity this is …
joro's user avatar
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5 votes
Accepted

On the search for an explicit form of a particular integral

High precision numerical computations suggest: $$c_1=73/5760 $$ $$c_2=3625/580608$$ $$c_3=5233001/1393459200$$
joro's user avatar
  • 25.4k
9 votes
3 answers
540 views

Why mpmath computes $\sum_{n=2}^\infty (-1)^n\log(n)=\log\left(\frac1 2 \sqrt{2} \sqrt{\pi}\...

Working with precision 500 decimal digits, mpmath in sage computes: $$\sum_{n=2}^\infty (-1)^n\log(n)=\log\left(\frac1 2 \sqrt{2} \sqrt{\pi}\right).\tag{1}\label{1}$$ We believe the LHS of \eqref{1} d …
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1 vote

Is there a closed form of $\int_0^\frac12\dfrac{\text{arcsinh}^nx}{x^m}dx$?

Conjecture: $$ I(3,3)=-2\, \left( {\it arcsinh} \left( 1/2 \right) \right) ^{3}-3/2\, \left( {\it arcsinh} \left( 1/2 \right) \right) ^{2}\sqrt {5}+{ \frac {3}{20}}\,{\pi }^{2}$$ This holds to at …
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7 votes

Is this combination of generalized polygamma and dilogarithm actually zero? $\Im\;\psi^{(-2)...

Edited Maple's $\psi$ disagrees with Wolfram Alpha and your integral, so here are some conjectures with both: According to Maple -- your equality fails with this definition of psi. $$ 24 \Im{\psi^{( …
joro's user avatar
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