MATLAB Function Reference Volume 1: A - E - Bad Request

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In this case, with integer arguments,
beta(n,3)
= (n-1)!*2!/(n+2)!
= 2/(n*(n+1)*(n+2))
beta, betainc, betaln
is the ratio of fairly small integers and the rational format is able to recover the
exact result.
For x = 510, betaln(x,x) = -708.8616, which is slightly less than
log(realmin). Here beta(x,x) would underflow (or be denormal).
Algorithm beta(z,w) = exp(gammaln(z)+gammaln(w)-gammaln(z+w))
betaln(z,w) = gammaln(z)+gammaln(w)-gammaln(z+w)
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