Combining two vectors in a pattern

Is there a way to combine two vector let's say

a=[1,2,3,4,5,6,7,8,9]

b=[10,20,30,40];

the resulting vector would be

result=[1,2,3,10,20,4,5,6,30,40,7,8,9];

Is it possible to do this without loops

Thanks

Answer 1

[Walter Roberson]

n = length(a)+length(b);
mask = ismember(mod(1:n, 5), [0 4]);
result = zeros(1, n);
result(~mask) = a;
result(mask) = b;