I'm trying to do the following sum:
NSum[((50000 - x) choose x)*(1/3^15)^x*((3^15 - x)/3^15)^(50000 - x), {x, 1, 4}]
But I keep getting an error saying:
"Summand (or its derivative) ((50000-x)\ choose\ x)\ (1/3^15)^x\ \((3^15-x)/3^15)^(50000-x) is not numerical at point x = 1."
Does anyone know what might be wrong?
Thanks
choose
? $\endgroup$n choose r
C(n, r)
? $\endgroup$Binomial
. $\endgroup$