Calculated variables in for statement

[remibreton]

Hi! I'm having trouble doing the following. I've been skulking around, but found no solace.

@each $a in (2, 3, 4) {
    @for $b from 1 to $a {
        property: calc($a + $b);
    }
}

This correctly returns property: 3 up until property: 8.

This, however, has trouble working as expected.

@each $a, $b in (1, 2, 3), (4, 5, 6) {
    @for $c from 1 to ($a + $b) {
        property: $c;
    }
}

it is even possible? calc($a + $b) does not work either.