#ES6 (Javascript), 79, 67, 65 bytes#
ES6 (Javascript), 79, 67, 65 bytes
UPDATE
- minus 2 bytes, by starting with i=2, as suggested by @ETHProductions
- Saved 3 bytes, thanks to excellent advice from @Neil !
Golfed
S=(n,a,i=2)=>i<n?S(n,a,a.push(eval(a[i-2]+"-/+*"[i%4]+a[i-1]))):a
Test
S=(n,a,i=2)=>i<n?S(n,a,a.push(eval(a[i-2]+"-/+*"[i%4]+a[i-1]))):a
>S(8,[1,3])
Array [ 1, 3, 4, 12, -8, -1.5, -9.5, 14.25 ]
>S(5,[0,1])
Array [ 0, 1, 1, 1, 0 ]
>S(9,[1,0])
Array [ 1, 0, 1, 0, 1, 0, 1, 0, 1 ]
>S(25,[6,3])
Array [ 6, 3, 9, 27, -18, -1.5, -19.5, 29.25, -48.75, -0.6, ...]