Problem 52462. Easy Sequences 1: Find the index of an element

@Ramon, if you are submitting a question on Cody for everybody to solve, it is recommended you put atleast 3 test suites, mostly so that it encourages people to learn and not hard code solutions.

Thanks, @Dyuman. There are now 4 test suites.

@Ramon, Wonderful!

-a+(1-(-1)^(n+1))/2 will be negative in the 4th test. I believe it should be: index(a-(1-(-1)^(n+1))/2).

This works fine in my MATLAB software. But not here.
Any comments, please?

function n = index(a)
for idx = 1:1000
b = idx*((-1)^(idx^3+1));
if b==a
break
else
continue
end
end
n=idx;
end