Question 908146
Natural Number, n.
p, first term, unknown.


p+(1)+(2)+more
p++1-1)*1+(2-1)*1+more
p+(n-1)*1+more, for n going from 1 to 25


{{{sum(p+(n-1),i=1,25)=600}}}


Using the formula for this arithmetic series,
{{{highlight_green(n(p+(p+(n-1)))/2=600)}}};
Solve for n.