@for $i from 1 through 25 {
    $row = abs($i / 5 - 2);
    $col = abs($i % 5 - 2);
    $delay = $row * $col;
   .element:nth-child(#{$i}) {
    -webkit-animation-delay:(#{$delay*0.05s});
    animation-delay:(#{$delay*0.05s});
  }
}